DOS 3.3 was great.
I used to run it on a IBM PC with a 20 MB HDD, 2 floppy drives, and 640K of RAM. I had different DOS 3.3 boot disks with different utilities and tools based on what I needed to do.
Yeah, but dos 4.0 was a disaster. Thank god for DR Dos or microsoft would have been content to stick with 4.0 forever.
Much of what I know now is because of the primitive nature of those early computers (irqs, dmas, memory maps, etc) and having to dive in and fix them and program them. Windows programming (when it first came out) was akin to programming on the bare metal.
I find that people nowadays have no clue what's going on inside the machine and I get a lot of "fix it" jobs from friends and neighbors.