It was bad. There was a dedicated site called lotusnotessucks.com or something like that. It does not exist anymore but here is an article about it: https://www.theguardian.com/technology/2006/feb/09/guardianw...
The boots on the ground cried "ugh, Lotus Notes!" in unison and just had to deal with byzantine key combos, nonstop client crashes/unresponsiveness, and moronic UI decisions some 3-person team made in like 1987.
I have opinions.
I don't recall the client having much crashing and unresponsive issues, but I do recall people finding the UI unintuitive compared to MS products, and of course the custom products built with Notes could vary quite a bit. But so does the web, particularly the early web.
But then you can say the same thing about people building Excel apps and that has been a selling point. Or Powerpoint presentations that people complain about but keep using.
>Lotus Notes is used by millions of people, but almost all of them seem to hate it. How can a program be so bad, yet thrive?
I think half the issues people have with AI today are simply because AI has seen just as much slop in the real world as it has "good, clear code."