Do not use their app, then set ad block rules to block whatever you want.

Use alternative YT front-end like Piped, Newpipe etc.

I could be wrong, but i thought i saw shorts on newpipe the other day.

I guess you are talking about mobile. There a several ytshorts blocker extensions for desktop browsers.

I used a Firefox add-on called "Stylus" and wrote a custom css rule to hide the relevant divs/elements. It's not perfect, but it's okay. https://github.com/openstyles/stylus

However, after the recent ad-blocker targeting by Youtube I pretty much just stopped watching Youtube entirely. I added my regular subscriptions to the NewPipe app on my phone and just watch what they put out.

The add-on I mentioned above is super useful to personalize my experience with other websites. Particularly online-shopping and other marketplaces that have huge amounts of whitespace for no reason. You'd be surprised how much nicer the web experience is after you add a few "margin: 0px;" css styles to strategic areas.

If you change /shorts/ in the URL to /watch/, it'll load the same video in the normal YouTube UI. I like that better because it allows for such advanced features as... changing the fucking volume.

(Shorts will keep the volume set as whatever you last changed it to in the normal UI, with no way to change it without going to a different ("normal") video.)

On Android you could patch using Revanced, there's a checkbox for shorts in the feed.

https://github.com/ReVanced/revanced-manager