How restrictive is Steam's "Discovery 2.0" feature?

Since the discovery 2.0 update Valve heavily changed which games you see first in shop and which not. You will get more personalized suggestions and see more games based on recommendations from your friends and favorite curators.

I am a bit anxious to get stuck into a filter-bubble.

So how does the "discovery" -system work exactly (based on which parameters)? Is my concern about the filter-bubble reasonable?

I believe it's based on what tags you look at most often. If someone were to look at games marked with Sandbox, then games tagged with Sandbox would be shown to them.