But the new YouTube ads that play before video are unexpected. And, for me, quite often a back button. After 6 seconds of watching the ad I usually don't care about the video anymore :/ (call it short attention span).

I haven't seen them, but if I do that's going to be the last time I go to youtube for a very long time.

You can skip them after 5 seconds.

Some of them. Others you can't, and you have to wait full 30 seconds. Given that what I want to see is usually 3-5 minute long video, it's pretty significant (10-30%) time.