How bad it is can sometimes depend on the content creator settings.

I follow a few that are mostly funded by Patreon not YouTube revenue now, they tended to have lower monetization settings enabled.

I have tried to watch some videos that had pre, mid, post adds enabled etc… On a medium length video you would get an interruption frequently.

I use ublock but even with that some changes used to cause videos to hang or fail to play when the ad was supposed to be running.

This, the all feed is a stream of garbage,porn and spam at times.

1Gbit fibre, they offer up to 3Gbit but I really don’t see the need right now and don’t have the hardware to take advantage of it right now.