Disable your yt history, it disables pretty much everything yt wants to push.
When I open yt I get an empty page with a search box, even clicking on the Shorts page it just says "Recommendations are off Your watch history is off, and we rely on watch history to tailor your Shorts feed. You can change your setting at any time, or try searching for Shorts instead. Learn more."
But that is unfortunately a nuclear option that should not need to be taken to perform such a thing. Like the op, I have no interest in Shorts, especially considering the type of content that seems to proliferate that format.
However, I feel like YouTube does a genuinely good job — at least for me personally — of curating my feed with videos I have genuine interest in; mostly being tech talks and home DIY.
I'd hate to lose the discoverability I currently have for the sake of having to disable a feature like Shorts.
I use youtube without an account, only a cookie which I can nuke anytime. My experience with this is as you describe; it does a great job of giving me videos relevant to my interests. If it ever goes off the rails, I nuke the cookie and start over; reseeding the recommendations by watching a few videos from high-brow channels like Applied Science. It recommends no shorts to me.