Hi! Welcome to the community!
The same way you get better at anything, practice.
Let me ask you, you said you want to get to a point where you can solo something, Have you tried it? If you haven’t then, How do you know you can´t? If you have tried it then, What do think you are lacking?
If you haven’t tried doing something on your own, I highly suggest you do, don’t do your dream game, do something small, like a Megaman Clone with just 1 level and 1 boss fight, maybe add 4 different types of weapons, and please, do not google “How to make a Megaman clone in Unity”, because you’ll find an answer and you’ll end up doing the same thing, copying someone’s code instead of writing it on your own, just go out there and create small games on your own, don’t expect them to be huge or amazing, just do things, and see where you are and what can you do with your current knowledge.
Maybe this will inspire you, when I started my game dev journey I took Unity’s official tutorials, they were like an hour-long, and there were like 4 or 5 of them, that was more than enough to build my very first game, you don’t need to know what a generic C# is for, or what polymorphism is all about, or about coding patterns, you don’t need any of that, you just need to start creating things on your own, that’s it. Don’t get me wrong, the more knowledge the better, but knowledge by itself is useless if you don’t put it into practice.