YouTube Music does not currently have a way to dislike an artist and/or to keep that artist’s music from being suggested or included in random/radio mixes. In order to work around this, I wrote a python script that uses ytmusicapi to dislike all songs by a given artist. This should keep YTM from suggesting them to you and inserting them into auto-generated playlists.
You will need to generate an oauth.json file for the script to use as your authentication to YTM.
The instructions for generating that are here.