As someone who has written and maintained an RSS aggregator for years, I can tell you that this jankiness is in big part because of how vague and under-defined the feed formats (RDF, RSS2, Atom) are, and how “creative” various websites are in producing feeds which are just barely standard-compliant, but also just enough screwed up to cause problems when parsing them.
It was a headache after a headache trying to get all the weird corner cases handled.
Mastodon does not need to scale well. Even if the userbase shrinks to what it was before the Big Twitter Exodus (or whatever you want to call it) of last year, it will be perfectly alright.
Mastodon was fun and enjoyable before. It does not need more users to remain so.