I find it interesting that the "constraint fosters creativity" argument gets mentioned in these discussions. Not because I don't think there's truth to it, but because it's usually mentioned in conjunction with external constraint, right? Such as a GM telling players "these races are off the table"; that's external to the players, and constrains their choices.
Does it do anything for their creativity? It may. Sometimes a player may need to scrap one idea in favor of another, or to ditch a favorite go-to in order to come up with something new.
But it also may not. Maybe they have a really compelling idea for a tiefling... and then they realize no tieflings allowed, and so they scrap it and make a new character out of necessity rather than excitement, which turns out to be bland next to the old one.
I'd say that the idea of constraint fostering creativity doesn't really have a place in the discussion. Or, at least, not from the player perspective.
I half agree and half disagree with this. From a player perspective what I see the vast majority of the time is that players have a bunch of great ideas floating around and will generally have one or twelve that fit the constraints.
That leaves the minority of the time being "inspires creativity" and "the player ends up with a bland character." I've seen both happen, but more often I see it inspire creativity. Many times, even though I'm in the group that has many great concepts hanging around, the limitations cause me to think about my character in a new way and I see something really great and fun that I never would have thought of otherwise.
The only times I've ended up with bland and boring characters is there has been too much constraint, such as coming to game night and being told that the group wants to play human mercenary fighters. If I'm not in the mood for that specific concept, it's going to be very hard for me to come up with something interesting and fun. That's when I'll push back a little and suggest that in a human mercenary unit there might be a cleric of Tempus(a war god) who fights and heals, or a ranger to scout or something and see if the DM/group is open to that sort of thing.
But what about GM creativity and constraint? Never really comes into play, does it? All these creative GMs and their creative worlds just disregarding any kind of constraint that player choice might place on them. No constraint on their decisions at all.
This I have to disagree with. Often the constraints are also on what monsters and/or stories are available to tell and those limitations sometimes inspire me to create something around those limitations, accentuating them rather than ignoring them.
As for players constraining the DM by what they want, that happens fairly often in groups of friends. If most of the group wants something done a certain way, the DM is much more likely(usually) going to go along with it. It happens in my long time game with my buddies. We're going to discuss something tomorrow before the game and hash out an issue that recently came up.
In a pick-up game with random people at say a game story or convention, I'm not going to bend what is established just to allow a single stranger to play his pet idea. I'm there to run this idea that I had and players can sit down and play what I have come up with or move on to something else. It's not the same dynamic as a weekly game among friends.