As a long-time .NET developer (since it was invented), getting into Unity (have been doing it professionally, full-time for the last 4 years) was a huge exercise in pain and suffering. They have their own ideas on how projects and their dependencies should be organized that don't align with the rest of the .NET ecosystem and, quite frankly, it's maddening.

It took me probably two solid years before I was making things in Unity that were any "good" (not dropping frames because of stupid stuff that Unity does like decoding textures on the render thread, not taking forever to load on startup, being able to cross-compile to different VR and AR systems without making massive changes to the application, etc.). After the third year, I had written workarounds for so many of Unity's built in stuff that I wish I had just started with my own game framework and skipped Unity completely.

Well, I guess that's not entirely true. I wouldn't have gotten my first well-paying, fulltime job VR without Unity. But from just a technology standpoint, it's been a major impediment.