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.