One of the biggest problems I have with Unreal is that optimizing it for your project can be very difficult. There’s stuff that impacts performance that you don’t need and unless you know the engine very well then it’s hard to figure out what you need to do to.
From what I’ve seen, small developers and hobbyists have trouble making games with Unreal that run well.
Some projects I’ve used Unity for because you can start out barebones and add the extra things you want so it’s easier to know what things you’re using that impact performance, but Unity doesn’t have their source available like Unreal so you can run into something that can’t be fixed without that.