was there ever a point in history when MS were known for anything other than producing mediocre (at best) quality software?

I know nowadays it's very commont to pick on Microsoft, but they've delivered quality products, and even if you don't like Windows (I don't love it) it's a pretty decent operating system with lots of backwards compatibility. Excel is great. Visual Studio is great

Visual Studio didn't hold up to its competitors in the past (Delphi) and doesn't hold up to its competition now either (JetBrains)

it's another fine example of MS software being mediocre at best

whilst modern Windows is malware

It really reminds me of that interview with Steve Jobs from the 90s where you can tell just how frustrated he is at Microsoft's success with what he describes as really "third-rate" software.