I'm not sure if I'm qualified to give advice, I've only been serious for a year now, trying to do solo-gamedev + youtube, and have gotten almost nowhere with it(3itch followers, 12YT subs). But I can say 1 basic principal I have found, that I guess should be obvious to anyone who's been doing this for a while: YOU GET WHAT YOU PUT IN.
Phoning something in is as good as not doing it at all, and even after something seems to be a complete failure, there's always something you can do to make things better even a little bit, even months after the fact. Don't just release something and see how it does, then be like "oh well, I'll try better next time" when you're disappointed with it's performance. A YouTube video is under performing? Spend a morning rethinking the thumbnail & tittle, then share it around on a social-media platform you haven't shared it on yet. A game isn't getting any traffic? Redo it's tags and maybe give it a clearer cover image.
Some time ago I spent a month or so making a really stupid novelty programming language that was terrible. I made a youtube video about it just cause it was kinda amusing, almost no-one watched it. I was burnt out and figured no-one really cared anyway so I didn't actually release the language itself anywhere. About a month later on a whim I spent a day writing up a manual for the language and released it onto itch.io(not sure if anyone else has ever released an esso-lang on itchio), and the page quickly got more views than my other projects at the time, and by proxy that video got lots of views(lots by the standards of a 12suber), and is still the most viewed video on my channel.