What you are pointing out is real and I think unavoidable. Math is just denser than most other things. A few high level things I've come up with while self studying for the past few months
- Focus on what is achievable. Learning difficult things is like building a tall pile of sand at the beach. You need a very wide base of experience to be able to climb high. Don't expect to learn algebraic geometry without mastery of abstract algebra etc. Reading research papers before working through relevant textbooks is a lot harder.
- Use quality resources. Some books are really good for self study at a less advanced level (Abbot, Sipser, Pinter) while others are bad or need more maturity. Research papers from earlier on in fields and further back in time feel more approachable.
- Try harder to get help from people. I have found reddit's r/math biweekly Quick Questions threads to be helpful for specific, advanced questions. Reach out to colleagues and acquaintances. There are people out there who love this stuff.
- There's no substitute for going back to school and taking an actual class with office hours and someone who will look over your work every week and correct your errors, it probably speeds things up 10x