I would extend that and just say all first party operating systems are shitty

Up to now, I believe, these systems were not first-party but built by the manufacturers of the infotainment systems. Now, Mercedes is taking this in-house to get it right and integrate it with the rest of the far more properly?

BMW's is alright IMO. Unorthodox in its layout but it actually works well with the center console knob thingy and has historically been low-latency even back when every other manufacturer had a 2 second delay for every action on their awful touch screens.

Of course even BMW's system is still going to end up being an overly expensive Android Auto/Apple CarPlay launcher because what people want is Waze & Spotify, not random traffic updates from last week & DAB.

CarPlay and Android Auto aren't car OSes though, they're merely an infotainment interface. You still need a way for the user to check the tire pressure, choose between sports mode and eco mode... Cars manufacturers could just implement the basics and let CarPlay/Auto do the rest but in that case anyone that doesn't have a compatible phone is stuck without infotainment, same if you run out of battery.

CarPlay and Auto being so good is somewhat to blame for first party interfaces being that bad though: why spend litteral millions on look and feel if you know the users who care won't be using it

Voice recognition is the most infuriating replacement for physical buttons.

Even with (more) UX engineers, it was incredibly difficult to get any development done. When I was in this space, management and contractors were incredibly entrenched playing political games to grow teams even bigger to get more funding. There was nobody with any authority using the thing end-to-end saying “this sucks”.

I'd be curious to read more about the context of this. It looks like there are soo many low hanging fruits for anyone with mid-level technical seniority to step in and improve the situation measurably. Scala isn't bad but sbt definitely has plenty of (avoidable in hindsight) footguns. The tooling ecosystem of Scala has also improved leaps and bounds in the last couple years. Of course that doesn't do anything to the seemingly disfunctional organization but like the engineering post it was, it didn't concern itself with it much.

Because Qt is actually better than those things?

While I agree that first party systems suck, as someone with neither an iOS or Android device I personally prefer something work rather than a screen that says "connect iOS/Android".