I guess what I would say is maybe instead of assuming, when you are on a web based or mixed scene it's probably easier to come to agreement at the start, post that in the scene or explicitly tag it, update as necessary. Probably easier and quicker than the alternative. It should be OK to ask instead of guess.
And yes for many people the timeliness is a draw, it is for me too sometimes. With people whom I really enjoy rping with i don't really care if it's slow. There are some folks out there that like to rp with me when I can't be fast too, and I'm very grateful that as long as things are disclosed I can in part not feel 100 percent like a collosal waste of their time and annoy them with the need for reassurance (it still happens).
For a lot of people ooc masque and discovery were huge draws. Now even in genres where that used to be the norm, it's not. Did some people quit mushing over it? I'm sure they did. Did other people stick around longer when they wouldn't have with strict masque? Yes.
There will always be people who never darken slow scenes, and that should be okay. There are people for whom mushing will again be accessible because of them too, though. That also should be okay.
But getting in the habit of communicating what you're looking for on pacing is a good thing, imo, even if its uncomfortable at first.