The name of the game in YouTube is niche. The more narrow the niche, the better. Why?
Let us say you have on your variety channel a video where you do a playthrough of Halo 54 computer game, another video where you prove that socialism works BUT it just has never been done right before, another video that shows your cute little kitten struggling to stay awake, and fourth video wherein you give a movie review of Wonder Woman 84. Great, right? A little something for everyone, right?
Wrong. Unless you're already famous, people (aside from family, friends, and co-workers/classmates) didn't subscribe to your channel because YOU are behind it. No, they most likely (that's 99.9999% of the time) saw your kitten video, liked it, and subscribed to your channel because of that video. Now take a guess what they're expecting from your channel when they get a notification of a new video from you. Something totally unrelated to the video they liked, right? Right???? Not right, right? No, they are expecting another kitten video. But what does your variety channel give them instead? Something they did NOT subscribe for. See any problem here?
So what happens when that new subscriber keeps getting notifications about other stuff than kitten videos from your channel. Well, in a world of rainbows and lollipops, they will just fall in love with you and your wonderfully creative free-roaming mind. In the real world, they'll start hating notifications from you and begin to view such a spam. And then one non-kitten video too many, they'll unsubscribe. That happens and you'll still have a "core" subscriber base BUT it will only be made up of family, friends, and co-workers/classmates. Oh and people who are dead subscribers. Dead as in they remain subscribed to your channel but never watch any of your videos. Not bad enough? It gets worse as YouTube's algorithm penalizes you for such low viewership of your subscriber base.
So niche and then niche even further. The further down the rabbit hole, the better.
Good luck!