Except when they violate civil rights (i.e. "whites only" deed restrictions are not enforceable, though they do exist), I think the answer would generally be yes. In some places in Texas, there is no zoning, only deed restrictions, Houston being the largest city where that's so, though that has evolved a bit and the city does have more say about land use than in the past.

Anyway, deed restrictions run with the land and are legally binding on subsequent owners in Texas. Buying land is agreeing to the contract implied by the deed restrictions. It's part of the due diligence of acquiring land in Texas.

Of course, governments can change the terms of that kind of thing in some cases. But, I suspect any honest reading of this situation would have required the city to go through a public hearing process so that the neighbors of the property were aware and had a voice in the decision, at the very least (but maybe even with that, their was a clear agreement to reserve the land for parkland, they shouldn't have taken the land if that wasn't an acceptable obligation). Property rights and contract law are pretty sacred in Texas. I lean YIMBY about a lot of things, but this gets my hackles up. It looks illegal on its face and shouldn't have made it through the cities lawyers going over this deal.

Edit: I should also mention that it is literally the neighbors right/obligation to sue in these cases. I've seen the argument that the neighbors of the land don't have standing. But, for deed restrictions, the neighbors are exactly the people with standing to sue over violations of deed restrictions. Cities in Texas are not obligated to enforce deed restrictions in most cases and most do not, Houston is one major exception to that rule.