Good news! yt-dlp already has sponsorblock built-in :-) Have a look in the --help text output for the "sponsorblock-remove" arg.

At the point where you're removing sponsor messages within a downloaded copy - of hope you're also sponsoring on patron or buying merch or something. There's a point where there needs to be some sort of revenue source to incentivize further content creation

just fyi, but this already exists via platforms like invidious, which is like a self-hosted youtube proxy that you interact with, and it dumps files to disk/etc. there are some other similar things already too.

not that you shouldn't use yt-dlp, because it's great!

and yes, as others mention - you can have yt-dlp use sponsorblock to cut out the ad sections too.

either use and nvidous instance that had sponsorblock(?) or use mpv with the sponsorblock script in your program