I found, when I tried to do this over a year ago, that no matter how much effort I put into "pruning" the home screen, YouTube would always devote ~10-20% of it to stuff I didn't want to see. Either it was epsilon-exploration, or stuff that tested well with the general population, or a bunch of "mandatory modules" like popular music or "news," but whatever it was, I couldn't get rid of all of it, and some of it managed to attract my clicks despite my best efforts. These extra items filled me with a sense of violation whenever I scrolled through.

So, I wound up using a CSS editor to block the main content of the youtube index page, as well as that column of recommended videos that gets shown next to the player. Here's my custom stylesheet:

.branded-page-v2-secondary-col > * {
  display: none;
}

ytd-browse[page-subtype="home"] {
  display: none;
}

ytd-watch-next-secondary-results-renderer {
  display: none;
}

Now when I visit youtube.com, I get a blank page, and have to click on "subscriptions" in the left column to get the user experience I want, plus I get recommended videos only when I FINISH a video. This is a far more pleasant experience, and I am able to use YouTube for pretty much only classical music, cooking tutorials, and the occasional education video, without ever getting pulled into things I don't want.

Speaking of the recommendation algo, btw, it's also super awesome. It has somehow consistently surfaced new classical music composers to me, and has played a major role in the development of my tastes and interests over the past few years. Without it, I doubt I would have been exposed to Schnittke or Bruckner, for example. Way better than spotify, and I haven't found anything to replace it, sadly.

I've also been doing this. In my experience, for it to be effective you have to be very vigilant about never clicking on anything you don't want it to recommend. The easy way to watch guilty pleasure videos is to right click > 'open in cognito'.