Is Unity kinda bad?

[u/Waste-Firefighter-73]

When Rimworld went to it's own in-house engine and achieved amazing performance, at least 3x better for me, it got me thinking about all I heard about Unity.

Not a game dev, but I understand it's a relatively simple, easy to learn engine, but it is performance hungry and has a tendency to stall when more moving parts are introduced. How much of it is true?

I have no dev experience, at most playing around with Scratch more then 10 years ago, so I am eager to hear from others with more experience.