Sure, there are significantly more players than steam numbers. The same is likely true of the OG MMO, EQ, which has 10 to 25 times the numbers of DU on steam.
EQ launched in 1999 and hasn't spent anything on advertising that I'm aware of for more than a decade. I didn't even know it was on Steam until a youtuber dropped a video "playing so you don't have to." So I ask, how good or bad are DU's Steam numbers? NQ may be able to maintain the current players count for a couple of decades like EQ, but that isn't growing nor pushing profits. I guess the real question is, what is NQ planning going forward? I would think EQ is still alive due to active development and new expansions but I could be wrong.