The thing is, if DS9 had been more popular in its time, they probably wouldn't gotten away with making it as different from mainstream Trek as it was. I seem to remember TV Guide praising it with words like "harsh" "gritty" and "realistic." Critically, it was praised, but it wasn't being watched as much as TNG or VOY at the time. If studio execs had taken more notice of it, they probably would've tried to dumb it down and made it another "TNG lite" a la Voyager - because execs seem to think viewers want more of them rather than something different that actually takes risks. Which is not to bash TNG or VOY, but there is something to be said for arc storytelling vs. stand-alone episodes.