I'll repent later.
Here's a test to run on Gmail web client: Mark an email unread or do anything that changes state. Now click the email, as to read it, and then close your browser. It will not let you because it's still "lagging" in the background for you. It's dreadful.
Calendar invitations are .ics files that any calendar client can consume, it’s a different remote protocol underneath too (caldav)
I'm using it as daily driver and wouldn't switch to webmail nor Thunderbird or Evolution.
As far as Evolution goes, I don't see myself moving away from it for now. I can't afford to have reminders not showing up, or have my calendar not syncing for half a business day because something has gone wrong. Evolution is the only program that I've tried that gets both of these right, and I've tried many, many applications both native and Electron-based.
Don't get me wrong, I'd switch in a heartbeat if I discovered a superior solution. But as-is, the few issues are found, aren't enough of a motivation to switch. A few cosmetic/UX glitches and nice-to-have missing features (highlighting background entries with their category's colour, busy/free/out-of-office setting on meetings) are tolerable when the alternatives are so, SO much worse.
But those issues are solved today (and since a long time by now).
I don't know whether Kontact could be considered substantially better than Evolution. But it works fine and has a lot of features not found elsewhere. It's also quite focused on power-users I would say. For example you have configurable one-keystroke commands for all important functionality (and being a KDE application you can configure shortcuts for actually every action if you like to). It handles big inboxes in different accounts (being capable of showing an unified inbox if desired) and independently of that multiple identities. The calendar and mail components handle Exchange idiosyncrasies. The GPG stuff just works.
For people looking for a true Outlook alternative on Linux it's at least one of the things worth trying. That's why I've mentioned it.
I'm actually not sure about this, Thunderbird to me seems like it's pretty good: https://www.thunderbird.net/en-US/
The only bloat that i can think of is the calendar functionality that i simply don't care about, but that's easy enough to get out of the way. Maybe one could also have gripes with the account administration section, though that's not necessarily touched in the daily usage.
Apart from that, it does everything i need, in the simplest way possible and is as boring as it is usable. Contrasted with lots of the modern day software, i'd instead put it into the category of "workhorse" software, where LibreOffice, GIMP, KeePass, Notepad++, SourceTree/Git Cola and others live - dependable pieces of software that do what i need without many breaking changes and all that many bells and whistles. The kind that you install and forget about, maybe updating them once every few years if at all needed.