Plenty of Googlers get thousands of messages per day and they use Gmail. There are filters and importance heuristics built into Gmail to help with huge volumes of email. To say "nope, you can't do it that way," flies in the face of reality.
I can filter out the stuff that I don't necessarily need to look at with GMail.
What I can't do is invoke programmatic tools on the web interface itself (at least not without learning a slew of web API stuff).
As opposed to being able to process my local Maildirs with shell tools.
How do you, say, generate stats or view diffs on 84,800 gmail messages? I can do that, trivially, with mutt (tags and commands/pipes) or from the shell outside of mutt.
I still find mutt's filtering notation (~f ~t ~N ~U ~d ... ) to be far more useful and far faster for most use-cases than GMail.
I'm accessing that corpus via both tools right now. Mutt is generally the more useful of the two. One of the advantages, again, of offlineimap is that I've got the option of doing either. And while I'll fully admit that there are some mails for which a full GUI client is more useful, plain text still wins in most instances. And even where I'm not in mutt (say, on an Android device), straight text virtually always wins.
I'll also admit to using GMail's filter rules to classify my mail, though they have problems, most notably the inability to un-archive specific messages, or to re-order / order filters at all. At least so far as I've discovered.
They're still generally better than Microsoft's pants mail rules.
Plenty of Googlers get thousands of messages per day and they use Gmail. There are filters and importance heuristics built into Gmail to help with huge volumes of email. To say "nope, you can't do it that way," flies in the face of reality.