Hi Andrew,
wrt "RSS is also the basis for syndicating my posts to places like Mastodon and Bluesky, which would mean rearchitecting my setup if I went down this route." As you use WordPress RSS can be used quite flexibly I think. E.g. having different RSS feeds for readers, sharing to Mastodon etc. (I have different RSS feeds for different comment streams, like including and excluding Mastodon likes/reposts from comment streams).

I currently do it the other way around though, I've architected what is on the site, not what's in the RSS. All posts are in my RSS, but a category (that contains the RSS-only postings) is not shown on the front page or in searches / overview pages.