No doubt BG3 is well polished and slick. They should with the size of their staff and the millions of dollars in resources. Solasta is bare bones.
Whether you like the UI and combat on both games is really determined by what you are familiar with. If you know 5E well, Solasta is better. Even the UI is better because it is intuitive to someone who knows how combat works in 5E. On the contrary, if you played DOS and not too familiar with 5E, I'm sure BG3 feels much more intuitive because it's set up similar to other CRPGs. And Solasta, when you are ready to attack, the system clearly shows what mobs are open for attack by drawing lines to your character. All the mobs. I've actually missed a few times in BG3 because I didn't have the cursor exactly on the monster because in BG3 you can target the ground next to the monster.
And by admitting you don't care about 5E is obvious why you like BG3 more. You want a graphically beautiful game with detailed characters and a compelling story (hopefully). That's where BG3 shines compared to Solasta; you're right it's not even close in this regard. Your opinion is perfectly acceptable and logical.
But I think Solasta is mechanically more sound but without the huge financial backing it will never look as beautiful as BG3.
Myself, to butt in here, I find 5e to be dumbed down and overly simplistic - 3.5e has the details I'm looking for. People who care about rules but with disdain for 5e - probably also agree that the careful attention to detail are also not too important.
The gameplay preview on Solasta is doesn't seem too impressive to me - because I'm looking at a game where there are long, narrow pathways that somehow popped up in a graveyard? I'm thinking they just mastered the rules and didn't care about providing an actual game from seeing that. That seems more restrictive than BG3s web of paths.
