I worked in places that did everything from comprehensive correspondence management to configurators for factory systems. It’s a pretty powerful set of tools.
The Microsoft world was much more primitive until the mid 2000s. GroupWise and Notes shops didn’t have the ridiculous mailbox size limitations that Exchange had up until about a decade ago. Even today, the dumpster fire that is SharePoint is arguably inferior to what Notes was shipping in 1996 in some ways.
That being said, I've work on a handful of installations of various sizes, including large state governments and Fortune 500 companies setups, and have never encountered one that wasn't a massive struggle to work with compared to just about any alternative solution.
The only open question is that will Teams, which is at it's heart a bizarre mashup of SharePoint and enterprise IM/Voice/Video will eventually engender the same universal disdain.
it suffered of development inconsistency if anything, much like java applets
turns out if some platform access is too easy, everyone starts publishing crapware