The other answer is that the people creating these ads have the resources to continuously try and bypass filters/moderation.

If there is filters/moderation.

There are, but only for using IP of large corporations. If you put 12 seconds of a major label song in your video review of an album, that video belongs to the major label now.

It's a lot easier to automatically detect a match to 1 specific thing than detect a match to a completely novel thing that offends sensibilities in a similar way to other things.

There are basically always filters of some kind, though not necessarily the ones we want. The bigger the target that filter represents, the more effort is spent breaking it.

The filter you want is named 'uBlock Origin' :)

Indeed, and the Revanced apk customisation on Android, and SmartTube on Google TV.

I've not seen an ad from Youtube for probably 10+ years on my devices (since whenever Vanced made the apk customisations popular).

Without ublock origin internet is so dirty.