Hey, there's your startup...video speed dating! lol
eHarmony is on the other extreme end where their checklist is 250 questions and the process is very tightly controlled!
Speaking of speed dating, I did actually give this a shout a few years ago but couldn't get it off the ground. Important lesson: don't go into business with friends unless you have absolutely complementary skills.
Several of my past partners have been people who would have ruled me out for various reasons, including "big" ones like race and age that would be high up on the list of first things people would expect to filter by.
So while they' reduce the pool of messages, chances are good they'd also rule out the wrong people.
It would be like that South Park episode. Naked guy, naked guy, naked guy ...
Let people sign up without filling in much to just browse. But at each and every step, show them some possible candidates that will be unavailable to them unless they fill in a bit more information.
"This pretty woman? She won't let you message her unless you fill in your birth date and it matches her preferred age range. Guy over here? Cares deeply about your music taste".
It's no different from how a lot of these services will suddenly hit you with paywalls to do various things. Get you fired up about contacting someone first, and then demand just a bit more.
Out of all the online dating sites I've seen/used I think they are the best by far.