Login to your Google account and access the activity controls.
Find the “YouTube History” section and switch off the setting. Also, make sure both the checkboxes in the section are unchecked — the first one is about the videos you watch and the second one is about the searches you make on YouTube. You do not want recommendations from either. And apparently switching the whole setting off does not disable both by default.
Click on the “Manage Activity” setting and clear all the activity. You can also consider setting it to automatically delete after every 3 months.
(And while you are at it, you should also consider pausing the location history tracking. This does not break any of the Google services.)
You can also make the “Cinema Mode” as default on your video controls. This should leave less space for related/similar videos recommendations from YouTube.
It is easy to get addicted to YouTube - unknowingly spend hours clicking through the myriad of recommendations that algorithms through at you. The experience sucks. I have been burnt many a time. So much so that I spent a month off YouTube this year. It helped.
But staying off YouTube completely is difficult. The above steps have helped me not stay glued to the app for hours. I either access the video directly (if I know what I want to watch) or browse my Subscriptions page (when I don’t know what to watch). The home page is useless without history turned on. And so are other recommendations. Trust me, you do not want them.