This is where we need to start harnessing AI for our advantage rather than corporations. Have it scan the videos as it buffers and automatically remove the ads.
comskip.exe does it well on free to air TV, but I suspect the methods it uses might not work so well for Sponsorblock etc. That said, maybe a hash can be made of the video every ten seconds, and when the playback hash differs, skip that ten second block. Computationally intensive I suspect, but might work for embedded ads.
Only works if google inserts ads without re-encoding the video. I think that's possible, as long as you only cut only keyframes of the video (shutter encoder has a feature to cut without re-encoding, and it warns of this limitation)
You could probably train something like that on semi-reasonable consumer hardware. Ads often have a very distinctive style and tone, and you need only a single output - the probability of it being any given second being an ad. It would probably take a lot to run though, you better hope the people who install the extension have good PCs. And, it would probably never get 100% accurate, you'd have to put up with still seeing some ads and having to rewind when it skips over valid video.
It's usually even easier than that... In my jurisdiction, ads have to be clearly labeled and identified. It should be relatively trivial to detect this label.