I could be mistaken, but I see Fediverse interaction as more organic/direct. A post without hashtags is a cross between screaming into the void (low follower count) and addressing a audience (high follower count) with your content ultimately being spread by word of mouth (Boosts). Adding a hashtag would be the equivalent of posting on a bulletin board or presenting to a special interest group. Those who want to know will be able to find your post easier.
I don't think it's advertisements that are disliked but the unscrupulous use of tracking data and the bombardment of information which we neither asked for nor want. The latter is the primary use-case for "influencers" in my experience.