Well I say something similar in the past, now have seen the GMail evolution path I change my mind, beside that I do not generally use webmails except when I'm with a machine without my environment, my main MUA is notmuch-emacs.
I also agree about TB, classic MUA seems to be remained in the 90's however at leas for us not-basic-users notmuch-emacs, mutt&forks, pine&forks, mu4e etc are valuable options, long to setup-up, mostly because anyone have a personal recipe and no one offer a ready-to-use solution, but far more powerful than any webmails.
However mailpie can be consider a good GMail-inspired webmails and IMVHO for most of mail users Roundcube even if is really basic it's enough, clear, simple and effective. Contacs are a bit limited compared to Google's one but the rest work well.
While I agree that roundcube is really basic when compared with Gmail, I'd say that if you follow the convention that Gmail is nothing more than a webmail client (i.e.: a place you access through a browser to receive, read and send emails) then roundcube is exactly that. No bells or whistles though.
Gmail isn't just a webmail client - filtering out spam is a major part of any mail service; a mail server that doesn't reliably throw out the appropriate 80% of my incoming email messages simply is not usable.
I could run a mail server myself, but I don't believe that I can achieve comparable levels of spam filtering without excessive effort, so I would need someone else to provide this service.
I also agree about TB, classic MUA seems to be remained in the 90's however at leas for us not-basic-users notmuch-emacs, mutt&forks, pine&forks, mu4e etc are valuable options, long to setup-up, mostly because anyone have a personal recipe and no one offer a ready-to-use solution, but far more powerful than any webmails.
However mailpie can be consider a good GMail-inspired webmails and IMVHO for most of mail users Roundcube even if is really basic it's enough, clear, simple and effective. Contacs are a bit limited compared to Google's one but the rest work well.