Young Griff/Aegon Targaryen technically would be Rhaegar’s first son, so Dany’s nephew (like Jon is). But there are some theories that Griff is actually a pretender (though he might not even know that).
Basically, he is a Blackfyre and supposedly Varys and Illyrio have groomed him for the throne. So even if he is revealed as not a true Targaryen, the people might not even care because they still love him. But you’re right, Dany’s actions would make a lot more sense if she was dealing with him rather than Cersei. I think the key is making it to where Dany blames the people to feel like punishing them. What you said makes sense, so maybe we can think of an alternative, like that Missandei idea I had.
But you’re right, even if we were to try to fix things, it still won’t be perfect obviously. But you know, GoT has still been a great show, especially the first four seasons with some good moments in the following ones. I guess I would want to try to make some changes that might make the show more bearable for those who have loved the show, but have been disappointed by the last season or two and think it might affect their interest in rewatching the series eventually.