It's really too bad that you can't disable YouTube shorts. I like watching YouTube videos on my phone, but the shorts is too tempting and I find myself wasting so much time with totally useless content. I'll probably have to remove YouTube entirely.
If you're an android user, try the Revanced App. I use it to eliminate all ads and enable SponsorBlock on YT, but it also allows you to customize a lot of the experience. You can turn off shorts by[1]...
1. Open YouTube ReVanced
2. Tap profile picture (top right)
3. Tap Settings
4. Navigate to ReVanced > Layout
5. Tap "Shorts components" at the bottom of the list
This may not apply to you, but the way I consume YouTube is by turning off history and subscribing to the creators I want via RSS. That way I seldom even remember Shorts exist; they simply do not appear for me.
If that wouldn’t work for you, consider removing the app and accessing YouTube via the browser. I would be surprised it there’s not an extension or blocker which can disable those.
I do this as well but find it a bit of a pain to add/remove sources since YouTube doesn't offer any easily accessible RSS feed. Wish there was a way to sync subscriptions with the YouTube account but at the same time I would never allow third party access. I refuse Google login on third party sites.
As latexr said you can disable watch history. This means there is no home page (even when it should have known my interests, my home page was awful so this isn't so bad). You don't get watch-progress memory on videos, which is simple to adjust to. Recommended are less targeted and I get a lot of the typical ragey youtube stuff but it is mostly half relevant. I no longer watch any shorts which I kept clicking just to "see how bad they are" until it became a habit. And the UI keeps pushing it... If youtube makes the no-watch-history method not work, I'm just deleting the app and waiting until I'm bothered to configure revanced.
If you're on desktop, download the Chrome Extension called "Unhook". It lets you hide stuff like Youtube Shorts and makes Youtube less impulsive. Very helpful for focus.
