This is why remakes are bad TBH.
It could've been a new DS game and it could've sold better because of that making future DS games possible.
Instead we've got a mostly pointless remake which didn't add anything of value to the franchise, sold poorly and has killed it again.
It selling better is completely speculative, though. As much as DSR didn't change enough (and I'd argue that changing the structure to allow free roam on the Ishimura was enough--arguably more of a value add than RE2R and 3R, which had serious omissions), I imagine a DS4, with zero of the OG creatives, while the OG creatives were making a new space horror game would have similar issues exciting the fanbase.
And like, a 4 might excite the fanbase, but the Dead Space fanbase was not significant enough to keep it alive back then. Giving us a chapter 4 a full decade and two console generations after 3 would lock out new people--and new people was what was needed.
Capcom had no issue grabbing new people. Both RE2R and 3R sold multiple times what the OG releases did (and the dreamcast, PC, and GameCube ports could not have been you substantial, as Capcom didnt provide tracking data for them), caveat being RE at its worst has always sold better than Dead Space. RE4R is the fastest-selling game in the franchise, and it's arguably the quintessential unnecessary remake, as RE4 OG still is readily available and is still making greatest of all time lists.
So the question is, if DS4 came out instead and failed, would we blame Motive for making a game that only the fanbase cared about, or for bastardizing a once-great series that really could've been brought back if they stuck to the fundamentals?