If you use Firefox Nightly (mobile) then you can:

1. Fully block ads with uBlock Origin

2. Block in-video sponsorships with Sponsorblock

3. Block all shorts permanently with Hide Youtube-Shorts

These 3 extensions fix your issues. There is also an extension to bring back downvotes. I do not use it but I think it is widespread enough to be useful as spam detection.

This also allows you to listen to videos with your screen turned off and gives you the option to have the video playing in a tiny screen so you can watch it while doing other things on your phone.