Godot 4.2 / C#. Godot is an amazing engine and I highly recommend it for indie devs. The iteration cycle is a few seconds. IMHO, using Unity will absolutely slow you down, as a designer/programmer. I can't comment on the reality of a 3d game with a complicated art pipeline, however. But for a game like Ballionaire, Unity or Unreal would have been a mistake.

Ballionaire was fun by day 3, the first time a ball dropped and hit a trigger that caused an effect. It was luck a bolt of lightning to me. I am a VERY pessimistic person. So the fact that it felt compelling that early, and like, anyone who saw it could understand it and felt the fun, was a huge sign to me. Unfortunately, not every game has a premise that allows for that. I don't think you could hope for the same kind of feeling while making a 4X for example.

But if you're making a game that ultimately should feel fun from moment to moment, like these kind of quick-play games are, well, I think you can get there quickly and with little work, if the idea is solid. And if you can't get it to feel fun, I would be wondering if the idea is solid, versus it needing more time/polish etc.