learning java properly to develop apps form scratch is an ambitious goal.
I would go with flutter like another user suggested, or unity for games.
A youtube tutorial wont even scratch the surface of what you actually need to know to make something popular (or that wont be cloned instantly if it does make wave). If you know the basics of java already, next step would be to learn about the model used on android ( not the standard MVC model used online ) and application state management (dont eat your users battery life). The hole is deep and wide, best thing to do is focus on what your end result is and work backwards, because the beast you a tackling people base their careers on and never stop learning.
Also, a major key to success is ASO, and user acquisition which most rankings are based on. ASO alone is very unlikely to get you downloads or rankings on the play store today, you need $$$ to play these days.
What you need is a creative approach in 2021 and on, thats where you mind should be, what's your edge...