Comment by grumbel

From my experience Youtube simply recommends more of the type of videos that you actually watched. Watch history overpowers basically anything else you do, your subscriptions have little to no influence. A single click on a 'wrong' video, and you'll get tons of similar ones in your recommendations feed for weeks to come, especially when you end up clicking some of the newly recommend videos. It requires purging unwanted topics from the watch history to actually get rid of them, which so far worked very reliable for me.