Isn’t part of presenting something like this to your players seeking constructive feedback?
If you want me to play with you in your setting, shouldn’t I have some say as well, particularly if you are expecting me to commit to a potentially multi-year campaign?
It is an act of seeking constructive feedback. And if the DM has done the work, then that player giving feedback should have done the work too. Can we agree that coming up with a character concept with a turtle race is a far cry from worldbuilding, or even building a small portion of the world, or even building a city, or even building a hamlet?
And once again, a DM that hasn't done the work - accommodate everything and anything. It won't matter. But a DM that has done the work, the player should accommodate everything and anything. This still leaves an enormous amount of room for character development. Sometimes, it seems to me, the player that can't accommodate is as stubborn as the DM who hasn't done the work and still says no.
It's very strange to me that players accept tons of limitations: class limitations (go ahead, make your 1st level wizard wear armor and use divine magic while using barbarian rage), racial limitations (Go ahead and play a titan or giant eagle), background limitations (go ahead and pick seven backgrounds and get all those skills and equipment because you're a 500 year old elf), time limitations (go ahead and start your medieval fantasy game with a belt of hand grenades, a machine gun, and two laser pistols), and spell limitations (go ahead and have all the spells in the PHB at your disposal, after all, it's all magic). Let alone accepting attribute limitations, DC limitations, damage and to hit limitations, and level limitations. But when a DM limits a race, it means they are not taking feedback? It's very strange.