I remember growing up, we used Outlook with our ISP-provided email addresses. The first time I ever saw webmail (it was probably Yahoo or Hotmail at the time) I was just confused. To me, web browsers are for browsing the web, and email clients are for accessing email. Eh, but what do I know. The article was interesting though.
I used to, but these days I switch between a work desktop, my phone, my home desktop, etc. So consistency of features matters. Also things like a "draft" I did on my mobile shows up on the web client on my Linux desktop, custom filters, signatures, are the same everywhere, etc.
The web and mobile-native clients for Gmail, Outlook, etc, work more the same than switching between something like Thunderbird and something else.
Having said that, I'd love to jump the Google ship if I could find any other mail provider that had a good app for mobile and had snooze, which for me is the killer feature for email.
And I have it on my phone, laptop, and desktop without any issues, giving me access to all of my email everywhere. Even when I'm entirely offline.
These days, I just don't really have a need for an email client, I do most of my emailing through my phone and don't use it as often as I did between 2008-2012 or so. Those were probably my heaviest emailing years.
Thunderbird could use some monetary support last I heard. And/or developers.
Gmail has a good webmail interface, but I only use it in dire circumstances. It is not my primary mail either.
Mileages vary.
Outlook and Thunderbird are not great. However they probably are better than the current Gmail webapp...
* Smarter filters: I can e.g. delete all twitch "streamer has gone live" messages that are 5+ hours old - they simply aren't relevant once the stream has ended.
* Bulk actions. When I get behind on my emails, I tend to sort by sender to decide what to do with 10s of emails at a time. e.g. I might archive a lot of older PayPal payment notifications by clicking the first one, shift clicking the last one and hitting archive. Gmail needs me to click each email to do so. Or search for PayPal, and do another search for the next sender I want to deal with.
Honestly nice interfaces for working on items in bulk have kind of vanished with the transition to web and mobile. Was looking for a replacement for Clementine with its Spotify support dead but the only options were mopidy front ends which sucked for bulk management of tracks in playlists.
* Expandable threading view. I can view an email thread as a tree of email titles and follow the flow. Gmail shows only a single item and then presents it as a flat sequence if I open it up.