Agreed with the other posts here.
2d ui is often more intuitive, more accessible, just easier for many devs, and depending on the genre and game design there may not be a strong reason to make everything 3d from a game play pov.
Besides, some 2d titles actually do still look gorgeous. 2d game engine does not always mean 'low res pixel art.' I've seen beautiful hand drawn 2d work like in indie title 'Gorogoa' and painterly work like 'Braid' or recently 'The Master's Pupil' and then there are my aesthetic niches which vary... can sometimes include handcrafted miniature art, I have an isometric minigolf game and a first person Mystlike puzzler, both of them are in the works and each one of those two done with realistically detailed large scale miniature art.
And then there are the many, many 2d engine games that still make use of 3d rendered art. So many old 90s games did this from Simcity 4, rollercoaster tycoon, The Sims, Starcraft, the original Fallout. Myst, Riven. Less common now as 3d is more attainable than it once was but still a valid dev route especially given the continued presence of lower end systems (mobile gaming) and the fact that it is possible to make a 2d game run and look beautiful on nearly any system. 3d games with that sort of fine, intricate art detailing will typically have higher hardware requirements as the cost of the added freedom of motion.
Now, some game developers on the indie side have done amazing stuff with 3d games.
I know a number of solo indie devs who made 3d games which look graphically amazing. Carlos Coronado, Danny Weinbaum and a number of others come to mind.
It clearly isn't impossible to do 3d art in a 3d engine really well as an indie, it just adds complexity and work. Danny Weinbaum spent over 7 years working on his "cozy, pacifist skyrim knockoff" - an open world game called Eastshade.
He made about 2 million $ in Steam sales from his project, another reminder that though 3d is harder in some ways, if you do it well it can also be worth it.
But it is always also a gamble, to some extent, what if those 7 years had resulted in a total misfire? What if nobody even notices your game after you have been pouring years into it?
There is something to be said for doing a smaller thing, a demo or similar, and throwing it out to the world game jam style as a way of confirming its core conceptual appeal. A way of checking if you are going off track before committing to a huge production. If the small example finds an audience, then it is likely the larger extension of the basic thing will too. And that is exactly what got eastshade moving in the first place, it is why Danny committed 7 years to it. Because he started with a little, modestly successful short project "Leaving Lyndow" and learned from that, that the sort of game world he was making appealed to a lot of people.
I don't have a demo, I am diving straight in (for better or worse) and just gauging odds of success based on whether people respond in any way to early imagery and material relating to my work.
Maybe that is dumb but I know even if my efforts fail I will be okay life wise so... I just realize that even if some of this fails hard it isn't the end. I have game asset collections gaining ground steadily and a successful Etsy print services shop. I have fallback, that is valuable. Don't risk everything on a gamble that could fail horribly. Have a backup plan!