@Thenomain I think of this kinda like the alpha/beta thing. Or a soft open -- when the basics are in, but everything needs testing and the flavor factor still has room to grow/expand/be fleshed out and people can have a real impact on shaping it.
By basics, I mean the following has been chosen: core type (MUX/Penn/Rhost/etc.), game system, general setting (target mood/era -- location can actually be more hazy than the other two but there should be an idea of what kind of location it should be, ex: big city, region, world-wide, small town), primary intended play style (PvP focus? Consent/non? etc.).
I don't think I'd, personally, drag a bunch of people into something and do the MUX equivalent of the old movie classic of, "Hey, guys, let's put on a show!" -- because a lot of the games I've heard pitched and brainstormed up amongst a crowd that no one's ever heard of because they never got past the brainstorming/creation stage started off the same way. (I've been involved in at least a dozen or so of those over the years.) No one's ever heard of them because they never got past that stage of development and died before they were known about more broadly.
Basically, it's just as easy for things to explode/implode this way as succeed, I'd think. Which is unfortunate, but thus far the record I've seen on this is 0/? against it working out. (I've never been on one of the ones where it worked in that stage to see what, exactly, they were doing or not doing; the one I was working on that may have survived was my old mortal/+ one, but I tabled it consciously/by choice when BITN emerged.)
I think this likely worked a little better before the entitlement and paranoia booms we've seen in more recent years, which is even more sad, when you really think about it. It kinda shows how pervasive 'we have seen the enemy, and the enemy is us' can be. As to the entitlement factor, just watching how much some folks flipped their biscuits over Echoes is telling. On the paranoia front, there are a lot of very vocal folks who instantly question 'how much was GrudgeBaitPlayer involved in the creation of this stupid policy/faction/etc.?! How do I know they didn't unfairly influence the development of this thing for their benefit?!?!?!' -- and such. It doesn't matter how irrational the complaint, or how ultimately ridiculous, because that shit breeds so much more needless paranoia and is ultimately draining as hell on the creativity and motivation in the end.