What are you actually disagreeing with mate? The point I am making is who is the rightful heir to the throne.
Gendry is Robert Baratheon's bastard son, That has been made clear
Gendry is the rightful heir to the throne whether nobody backs him or the whole of Westeros does!!
The whole of Britain may hate Prince Charles and not want the big eared prick to be king. But unfortunately he is the next in line to the throne. Simple as that.
Oh, with your initial point/wish about the spanner in the works. I don't think there's any possible version of events where he would emerge as a challenger for the throne.
And it's quite different to the Charles situation, because Baratheon rule of Westeros has lasted < 20 years. They were seen as usurpers to the throne by three of the nine major houses of the kingdom, with Lannister and Greyjoy largely not participating. The Targaryens are still loved and seen as the rightful rules of Westeros by a lot of people. I don't think any such analogue exists for Britain?
I agree with you that there are not a bunch of equally good claims from Lannister, Greyjoy, Baelish et al. Obviously there are not.
But arguably, the most rightful claim to the throne comes via the Targaryen children - Dany and Jon, rather than through the Baratheons. That (as well as dragons) why the likes of Tyrion and Euron Greyjoy are going to Dany. That's (plus revenge) is why Dorne has stayed in the Targaryen corner through the Robert Baratheon years til now. That's why Varys has continued to work for their restoration throughout their twenty years in exile.
Five (story) years ago, if it emerged that Robert had a bastard child, then that child would be a real threat to his (Jaime's) other children, plus Renly and Stannis. Then the Baratheons were still firmly installed as the rulers of the land. Now, Westeros is in turmoil. Yeah, there's a bastard child of the guy who overthrew the ruling family of three hundred years out there, but at this stage, so what? The kingdom has been ripped apart by five years of war, the ruling family is coming back, and everyone with an army already has a guy or gal to back.