That’s the separation of powers at work, which is desirable. Congress has to (and can) do it. Obama, unlike Trump, would sometimes back down when he met the edges of executive authority. That’s how it should be.
I wanted Gitmo closed, but I don’t want it closed in a way that further expands the executive branch by once again nibbling at the edges of another branch’s authority.
At ~all times for a long period of time during Gitmos operation, there was at least one (revolving) prisoner that no nation on earth would take. I think that was the biggest challenge for someone who actually wanted to close gitmo, to close it. Not clear where you would put them that wouldn't be yet another prison.
I guess now that the US has normalized relations with the Taliban, maybe they'll end up sending them to them, not sure who else will take the last ones.
Plenty of countries that are well-run democracies don’t have separation of powers between the legislature and the executive — the UK is one of many examples.
Separation between the executive and the judiciary is important, but separation from the legislature doesn’t really seem to be.
Even among countries that do have such a separation, the US is unique in making it so difficult for the legislature to pass anything, which IMO is the most serious flaw in its system. The permanent deadlock is what creates such a temptation for the executive to circumvent the rule of law and try to seize power wherever it can.