Compared to Unix and especially modern operating systems DOS is more comparable to firmware than OS, it was something ultra minimal which basically got out of the way of developers. And being so minimal it allowed IBM PCs to sell for prices below $10,000 (1980s! dollars). This was they key to the success of Microsoft and the IBM PC. You might have created a ‘better’ OS at the time, but no one cared about your fancy slow OS which used all the memory cost a fortune in hardware.