All this is true but mailing lists UI sucks. Please tell me how you navigate a tree of messages? It is not easy to tell who is this responding to and who responds to it. Yes, it can be figured out but why does the tree change as I navigate it? [0]
"Just use mutt" as a reply to "I want to read this one email thread" is rather missing the point. Plus the reality is most people neither use nor want mutt. Many people think the UX on mutt is horrible. Nice if it works for you, but it doesn't for many. So there's that.
https://lwn.net/Articles/875239/ https://blog.gnoack.org/post/lei/ https://people.kernel.org/monsieuricon/lore-lei-part-1-getti... https://b4.docs.kernel.org/ https://github.com/mikwielgus/forum-dl
If you’re downloading mbox files, then you know how to handle them.
The https://lore.kernel.org site is actually fairly decent, but limited to Linux kernel stuff and some adjacent projects. Gmane was quite nice too, but now defunct (the web UI anyway).