I think you also have to remove subreddits that the member is not part of showing up in search results. Several very niche subreddits I participate in have fairly regular low-quality posts by clueless people who just stumbled across them in search (usually looking for something related but different). The bar for searching for a term and posting in the related subreddit is SO MUCH lower than the bar for finding a forum in a web search, signing up for an account, and posting. It might sound minor, but it's not.
Keep in mind that I only felt what RattlesnakeJake experienced recently, years ago (before 2020) even though Reddit had the same front page it has nowadays, I did not experience so many random users posting useless things about posts, some even saying that they are just commenting random things "because Reddit pushed a notification about this post for me".
So it is not a issue with the front page per se, but the vibe that Reddit started fostering, especially after Reddit dropped the third party apps.