Pathfinder was to get around WotC dropping D&D 3.5. Paizo was started by veteran D&D writers to sell adventures, which they still do as adventure paths, rather than a system. When WotC updated to 4e, meaning no more print books that Paizo could reference in their adventures, Pathfinder was a way to print new 3.5e PHBs and Monster Manuals.

Paizo didn’t initially change much in PF1e. There were a few balance tweaks. The books were better laid out than 3.5. The players did the math on things like combat maneuvers in advance. In practice the game played pretty much the same, my groups jumped over seamlessly.

Having run and played both, I do think Pathfinder 2e is counterintuitively simpler in play than 5e D&D. 5e plays fluidly almost immediately, move and act. PF2e is pretty demanding for the first hour or three, the three action economy and Conditions (tm) are an armful, and many players need to unlearn some D&D habits. Once a player has below average system mastery PF2e is as fluid as 5e. Beyond that PF2e shines. The rules scale better to complex scenarios, giving players more clear options of how they could act and giving the GM a better framework to figure out exactly what someone needs to roll. I also think it’s easier for players to go from average to good system mastery in Pathfinder, it’s mostly just learning how to optimize their character and learning more conditions and spells that work in the framework the player already understands.

For new players in session 1 D&D is simpler, in session 5 Pathfinder pulls even or maybe ahead, and in session 50 Pathfinder still sort of works where D&D falls apart.

PF2e character customization, though, is much more complicated, which some people like and others do not.

Eh, yes and no.

Pathfinder 1e was pretty much just straight-up continuing D&D 3.5e, but with some tweaks. Pathfinder 2e overhauled a lot of stuff, often simplifying things, but still pretty complex.

Compared to D&D 5e, Pathfinder has more rules, but those rules often make things easier, or (IMO) get you more return for the effort. So, for example: The feat list is bigger and more complicated, but in practice, it means you only need to look at a handful of them when you level up, which is easier (and the rules give you guidelines for swapping things out if you don't like them). The monk has more decisions to make with stances and attack types, but that's... kind of what you want with a monk to make combat interesting. There are rules for boats, and holy shit how does 5e not have rules for boats.

The last example might sound silly, but it's part of what convinced me to switch. It's an annoying omission in and of itself, but also speaks to a broader pattern of 5e just not supporting Dungeon Masters, letting them fix the either broken or incomplete rules, or else take the blame for them. Pathfinder actually supports ~~Dungeon~~ Game Masters, as though their time, effort, and fun were just as valuable as anyone else's. /rant

Pathfinder 2e is what I'd play if I wanted something like 5e, but runs differently. If I wanted something similar, I'd pick something else, but that's a longer, even more off topic discussion to go into unprompted. :P

Pathfinder was created as an updated version of D&D 3.5, which was very complex. PF food streamline parts of it, but ended up just as complex at some point, mostly due to the massive variety of options available through splat books.

Meanwhile, D&D 5e was released to be much less complex by getting rid of stacking bonuses and the vast majority of math.

Parhfinder 2 (which I have not actually played yet) did not do that. They opted for streamlining the existing system by combining several similar subsystems into one (i.e. everything is a feat now). But the math is still there.

Yes it is. Pathfinder made for builders who want to create a character with hundreds of options to choose from. It is rule heavy in the tradition of dnd 3rd edition. Pathfinder 2e is much more refined, but I doubt they went away from this philosophy. It's still very rule heavy.

I hated the magical + physical armor parts in the D:OS mechanic. I think using a DnD ruleset instead of their own helps BG3 mainstream success. This is anecdotal evidence but I have a friend that is unable to play D:OS2 but loves BG3 very much.

They use the Pathfinder 1e rules which are way too complex IMO. There's no PF2e CRPG out there.

I don’t really think it is possible. FATE rules do not contain a game in a traditional sense and the game itself is created during play via Aspects. A computer game that attempts to do FATE right would just end up with a FUDGE adaptation. Maybe when the LLMs are much better…

Forgotten realms is basically the IP for standard fantasy. This is an enormous strength for an IP. Divinity doesn't have this strength, it doesn't speak naturally to everyone like this.

I played em both and even did a secret ending run. Love both but it's based on PF1e and it's still built with RTWP by default. I love the various origin characters that Larian made for BG3 and D:OS2 that made your party members feel like real characters that have their own motivations unlike other RPGs that have your companion to be more like henchmen.

PF2 quick highlights:
Action economy. You get three actions and can spend them however you want. Attack three times? Sure! (Note: there's a -5 penalty for the second attack and a -10 penalty for the third attack on the same turn (note: some feats can mitigate this eg. one that drops them to -3 and -6 respectively)). Move three times? Yeah! Move attack move? Attack move attack? Cast a spell (typically consumes two actions) and then attack? Sweet. Got a feature on your spell where you can funnel more actions into it for a bigger effect? Very cool.
Degrees of Success: Roll more than ten below the DC? Oof, that's not just a miss, that's a miss where you also fall on your ass. Ten or more over? That's a critical! You get sweet (and clearly defined) bonus effects. Roll a natural 20 or 1? That bumps you up or down a success tier instead of being an automatic failure or success. You might just be turning a critical miss into a regular miss on a 20 (given extreme DCs) or even a regular miss into a hail mary shot, like Bard hitting that gap between Smaug's scales.
Counteract as a broad mechanic: Counterspell is now just one implementation of a greater and robust counter mechanic, wherein you make a bid and possibly get a better result. The counterspell example is that you can counter a spell of up to three spell slot levels higher than the one you spent just by rolling high (see degrees of success above). This is also how you disarm traps and dispel auras.
Counterspell itself gets way more granular. It is very different depending on which class you're pulling it from, which means it feels way more satisfying, not having been smashed into a one-size-fits-all shape. You can build it up with feats, playing with the resource economy and requirements. My personal favorite is a feat which allows you (GM's discretion) to counter spells with thematically relevant spells, like fizzling a fireball with create water. It's intricate, it's interesting, you get way more control over your kit, and you get to feel really cool when you do cool stuff. Which applies to the system on the whole.

There are consistent rules that are written out pretty verbosely. This can be scary at first but also ‘generally’ prevents a lot of table discussion. There are tons of characters choice and it is pretty hard to make a low power/high power character; also encounter/monster building rules actually work. Price of this is that there are a lot of options that were balanced out of their fun. Thankfully they have been getting better at this.

Personally I think 5e sits at a weird point. There are games like PF2, 13th Age, etc. that deliver better gaming frameworks with depth and there are better ‘simple’ games like WWN and numerous retroclones that provide the bare minimum and empower GM to improvise. Where as 5e has had an approach more like the former to the rules interpretation and character complexity, with tons of unofficial official rules clarifications and specific character, while having the actual rules written out more like the latter group providing very little guidance to how to use them. It awes with fun abilities yet provides little on how they interact. It is not a bad game if the GM knows what they want out of it, but most games I have been in was a disparate mix of ‘things others do’. A lot of the blame lies with the DMG.