Solasta does a few things right.
- It demonstrates that combat according to the 5e rules can be fun and exciting without needing a ton of homebrew stuff in.
- The dice rolling system is clean and understandable.
However, as early as I am into it, Solasta doesn't seem to have a lot to do outside of the combat, and it seems quite linear, with little emphasis on roleplaying and choices. BG 3 is much more solid in that area, with far more reactivity. It's also lacking race and class options, and unlike BG 3, those won't be added in later.
So while there are lessons which could be learned, there's no point in exaggerating and ignoring the things which BG3 does better than Solasta.
I agree with you here. Combat looks to be so much faster, more smooth flowing, and more fun than it is in BG3. As someone who hates TB combat, Solasta's combat I can actually live with, unlike BG3 combat which I hate.
Your second point is correct too, though one needs to keep in mind the differences in the budgets of the two games which has a very direct impact on precisely this point.