I suppose you think it fitting that we should give up Guantanamo Bay because the current Cuban Government does not want us there.
The mistake there was ever allowing that communist dictatorship to get into power there. Thanks JFK!
The government of South Carolina ceded the property Sumter was built on to the Federal Government. It was no longer South Carolina property.
Just because the Government of Cuba that signed the lease for Gitmo no longer exists, does not give the current government of Cuba any right to Gitmo other that agreed to in the treaty. I suppose If the current Cuban government tried to take Gitmo by force you would be okay with that.