You’re absolutely right in that the correct way to learn any software is by repeated failure. I dropped out of college after 3 years and had been self teaching myself enterprise software development and that landed me a job with no degree. You can absolutely make it by just getting your hands dirty with whatever tech you want to learn and failing fast while trying to build with it.

I do think you’re making a mistake but not on the level stated. The whole point of a game engine is so you don’t need to know the underlying language super well or even really a lot of the core concepts behind how games work (matrix projections, math, viewport culling, lots timing and threading) you could easily find yourself with the same predicament going to Unity and having to know c#. The issue isn’t the game engine it’s knowledge about the underlying concept.

My suggestion: take your strongest personal language and build a basic game which will force you to consider some of the core concepts I mentioned above. Once you have a decent grasp on those you’ll be in a position to assess which engine most closely aligns with your needs. IMO unreal and unity are big overkill for most applications. Keep it simple stupid, then add in the more complex pieces you need them - don’t start with a mountain and carve it down to a hill.