Microsoft in the 90s was doing things that hadn't been done before with Windows. And the NT line, converging to consumers at XP, solved many of them, and by now they don't have an excuse any more.

I’m genuinely confused about exactly what Microsoft was doing for the first time.

Not the first gui.

Not the first web browser.

Not the first spreadsheet/word processor/slideshow.

Edit: I’ll give credit, NT is good kernel, and had some novel qualities.

I would argue that they where tge first to try and do all that at once while on non-specified hardware systems. Yes Apple, Amiga etc will similar stuff but they at least had set target hardware.

Microsoft tried to do everything for better and worse on wildly varied commodity hardware.

The first one that pretty much anyone could use and was useful for them. We credit Apple for popularizing the GUI, too, even though they stole it from Xerox.