When I got the XSX recently, it was so I can play Starfield when it comes out. That was basically the only reason. I did not realize the extensive backwards compatibility that this thing has. But since getting it, I've been playing FF13 trilogy, Fable games, Dragon Age series, Lost Odyssey, etc. Basically all games of note going all the way back to the OG Xbox will play on the latest console. Either with the original disc, or you can even purchase them online.
The point of my post is I think it's a real travesty that PlayStation doesn't do this. I don't understand it. First of all, you cannot buy most PS1-PS3 games on the digital store. You can't use the discs. The main way to get access to these games is through the top tier of PS+. But the selection is quite limited, and PS3 games in particular are streaming only.
With the selection, I want to point out that you can't even play most of the Killzone series on PS+. This is a first party title. There is absolutely no reason that Killzone shouldn't be available. Killzone 1 isn't even on there. A PS2 title that is not graphically demanding.
As for the streaming of PS3 games, maybe this was justifiable back on the PS4 because the PS3 has a unique architecture that can be difficult to emulate without performance drops. But with the capabilities of the PS5, it's not credible to claim that it can't emulate a PS3. It certainly could, if Sony wanted to assign resources to make an emulator.
I am not a fanboy of one or the other, and I probably still play more on the PS5 than my Xbox, but I think Microsoft should market their backwards compatibility superiority a lot more than they currently do.
This, coupled with the fact that Sony doesn't really need to make an effort (for the time being) are some of the biggest dampeners against modern BC. You also have to think how the Backwards Compatibility would take place. Physical media has been steadly killed and/or degraded in the past few years, and there's basically no chance of a reprint for games of the past generations. That would leave publishers with the only option of hosting those games digitally, but how many would be considered "worthy" of that cost? We can all think of certain big names - Symphony of the Night, Metal Gear Solid, classic Resident Evils - but the list grows thin very quickly. I'd love to go back and play a few hours of Legend of Legaia but how many people would also be interested in that? Furthermore, how much would a PS1 game be genuinely priced at? $5? $10? That's an irrelevant pittance for any major company, and I can't imagine the average consumer paying any more.
Its a sad reality, but I believe in the current capitalistic modern world, the Playstation Plus Deluxe is the most realistic, feasible option for Sony's backwards compatibility: Have the few genuinely interested die-hard fans pay an extra for access to classic games, while being mostly backed by a much larger demographic of players who are subscribed to the cheaper tiers.
(And let's be honest: I can also emulate Legend of Legaia very easily)