I think the idea that limitations breed creativity is orthogonal to the restrictiveness or not of the DM.I think some degree of limitation is healthy for creativity, for both players and GM. And I think that a GM should be free to create as restrictive a setting as they like, but it is on them to pitch that setting to players and get buy in.
Suppose I, as GM, pitch 5 campaign ideas to my players. One of them is an Undedark campaign with a psionic flavour with heavy limitations: only races available are Underdark races, no prepared spellcasters. (BTW, this really happened).
The players’ creativity can absolutely be stoked by limitations without the DM being restrictive.