Essentially, when people think back to how responsive computers were "before windows", they are recalling computers which had no networking, and disks which were so slow that you would never write software which depended in real-time on getting that data from disk. You'd pre-load all the data you needed into your meager RAM and then, yes, for doing the one thing that was loaded into memory, with the data that was already in memory, the computer would be very very responsive. But when it came to saving or loading, you could go and get a coffee.
I have to say that in this case you're wrong. The Apple Mac Plus in my parents' closet, which I still fire up from time to time to play Dark Castle (https://www.youtube.com/watch?v=KCkbp4wurW0), had a zero latency mouse (or at least imperceptible) with zero flicker. Took Microsoft at least 20 years to get something comparable. This is not a nostalgic mis-memory, or an exaggeration. Please find an old Mac from the 80's and simply move the mouse around.
> they are recalling computers which had no networking
The very first network games I ever played were over AppleTalk on a Mac, like NetTrek (https://www.youtube.com/watch?v=Z40VMsXtl0Y ... yes, that is digitized sound out of a 1984 machine), Maze Wars (https://www.youtube.com/watch?v=PoEpgfTtUYg) and the venerable Bolo! (https://www.youtube.com/watch?v=Bz_gYZ5kMvc), the latter still one of the best multiplayer gaming experiences I've ever had
> Sure, nearly-bare-metal OSes don't soak up much in the way of resources, but that only works in very narrow market segments, and computers are totally mass market now.
And we had Amiga. And BeOS. And Plan9.
All of which had very good latency. All of which Microsoft displaced with monopolist behavior and marketing money.
Microsoft is only interested in fixing the problems they caused now that they aren't the 800lb gorilla anymore.
And in any case, you mean "before Windows" if anything, because DOS was fast as blazes (and did pretty much nothing as a consequence).