It's not about how many people there are, let alone how often they post, but WHAT they post and IF it's anything of one's interest.
Not only I ignore a lot of categories, I also block people who only post stuff I don't care about. I don't mind seeing less posts and having less topics to interact, it's better for me this way.
Bear in mind that there is a Recent menu where every post from every category is available in order of last interaction. Everything shows up there, except for the categories you have chosen to ignore.