I think what makes me like the mailing list over RSS, even though it seems like a more low tech solution is that mailing lists are a curated/aggregated version of the content (often with annotations) whilst the RSS is a "raw" stream of data.
Ideally it's done by the person - so you see most important highlights. Aggregated by topics, etc. Alternatively things can be auto aggregated by topics if it's a discussion or by top popularity if it's like an overview of a forum /etc
as a consequence, it makes me wonder if it's possible to use some magical machine learning things too automatically curate topic you're interested in. And, like, build mailing lists or summary pages from RSS feed.
can be solved with AI filter + summary thing? project idea
feed rss feeds, subscriptions, etc
get a filtered/summarized newsletter?
give feedback on how much do you care/don't care about things to further train the model