I'll never understand why YouTube allows their ads to be trivially bypassed like that, instead of just making them part of the video stream. It would ruin YouTube for me, so I'm not complaining.
This is often done in fun ways where the ad is integrated into the content of the video, so it doesn't annoy me too much and can actually be a fun break from the content of the video.
But for the videos where it _does_ annoy me, I use SponsorBlock [0]. It's an browser extension that lets its users mark certain sections of a video as "ad", "sponsor deal", "self-promotion", etc. to effectively build a crowd-sourced database of ad sections in YouTube videos.
The database is shared and used by the extension to skip the marked sections on most videos I've encountered.