This. I kinda hate, but still understand, the general offlineimap/notmuch philosophy in this space. I am not in a bunker, I am not optimizing for a situation where I only have internet intermittently. I just don't want to leave emacs if I dont have to and want to be able to be quick and seamless between my code, mailing lists, rss feeds, org mode, and email in general. It was hard won, but I do get this with Gnus now. And yes, love how you can hijack almost all the IMAP/gmail niceties this way with a little bit of work, especially search.

One thing I have done is export the mbox archives of my old gmail accounts and keep them around in Gnus if I happen to need to search through old emails.