Yep, whenever I start a new job I say "Don't worry, because iamverysmart, you don't need any Microsoft products!" I am then hailed as a genius, everyone claps, and I get a big fat raise.
The snarky „just don’t use Exchange, duh!“ doesn’t either. It’s a non-solution that armchair experts provide, who aren’t responsible for managing mailing for lots of people.
There are many environments where people don’t have a choice but to maintain what is in production.
Whether or not viable alternatives exist, those alternatives don’t magically change org structure, office politics, budget, current business priorities, etc.
Bottom line: many people managing exchange don’t have the luxury of evaluating this problem in terms of alternatives.
I don’t know any that come close in functionality, configurability, and maintainability. Exchange scales from a one-person handyman to Fortune 500 without a hitch, it comes with an office suite and cloud storage space, you find specialists for it on every corner, and it mostly just works. That’s pretty hard to beat, even if I’m personally more than unhappy to be so dependent on Microsoft, a US product, and closed-source software; there’s just not much I can do about it.
Thing is, I’ve been doing this since before Exchange Online, I know.
People used a few different groupware solutions, worked with bespoke IMAP installations on Linux servers, or (the vast majority) had on-premises Exchange servers running locally. It all required lots of tech wizardry, tinkering, duct tape and hope.
It was a long while before we had turn-key solutions, and you needed actually knowledgeable folks running your IT operations, and nothing was as fully integrated or cheaply available as Exchange Online.