We shall see, if there is any improvments, when the new search features roll out. At least there were hints, that they are working on some things. The suggestions in the search box were the beginning.
Always funny, when people complain about the lewd stuff. Is there not a check box, they had to click to see that stuff in the first place? ;-) (It is funny, because there are several identical complain threads for the mature content - content people clicked they wanted to see and forgot they did so)
There is the old method of adding a single exclude to the search. Hence that thread about multiple exclusions. Single exclusions are possible, but not very user friendly.
For a more client side and manual approach, there might be something coming up, for Chrome users. I am nearly ready to release an unofficial extension, where you can filter out stuff. But it does not work on tags, but you can use it to have a similar effect.
Basically you would navigate to the tag you do not want to see and click through the first few pages on browse to collect the most popular games. A few hundred will be enough, so maybe 10 page scrolls. Rinse repeat for all you do not want. And then add the stuff you already have in your collections. For new popular games you can add them one at a time.
I believe a better approach would be to just add all the stuff you do not want to see one by one, if you did search for something you like. Especially the popular tags like horror and visual novels are often added for things that barely qualify. So blanket ignoring those tags might not what you actually want to do.