FWIW, many email clients -- before Gmail dumbed down email forever and no one seems to understand that email replies form a tree anymore -- also had (and maybe some still do?) that way of viewing the world.
Text: Mutt, Alpine, and emacs's mailer off the top of my head. There's a listing of other clients here: <https://www.tecmint.com/best-commandline-email-clients-for-l...>
GUI: Sylpheed, Thunderbird, KMail (KDE's Kontact suite still strikes me as one of the best I've encountered), Evolution, and Clawsmail.
My own strong preference remains mutt, and the ability to process huge amounts of complex email reasonably well is still utterly unmatched.
And some additional sources:
https://www.dennisc.net/writing/tech/gmail-aerc
https://www.julioloayzam.com/guides/email-with-aerc/
My simple config and binds that are a little bit more "vim-like":
More often than not, nobody will reply, so all threads are just one or two levels deep. Or in the rare case someone actually replies to an interesting point, it's usually not the original poster. Probably because they had no idea that anyone had even followed up on their post.
Requests for elaboration mostly go unanswered, and comments are made expecting no replies. So people just shoot ideas into the void, with interesting interactions only happening when someone famous comments.