Greyworm or the Dothraki not executing him or Jon on the spot doesn't make much sense to me.
The two directors decided that only they would direct the final episode (in order to avoid leaks). They would use no assistants. I think that is why the episode was disjointed.
I shouldn't say it sucked. It was good but not great. But most of all, I can't believe that I spent the past decade watching the show for an ending like that.