Except we know for fact that the Tevinter Old Gods are Dragons, and 5 are dead. We also know for fact that Solas is Fen'Harel, and he isn't a dragon. This and a couple other "theories" are just like the Indoctrination theory that people so adamantly convinced themselves of back in the ME2/ME3 days. We saw how that turned out! 
Yeah but Mythal , an elven Goddess can shapeshift into a dragon.
And there's a couple of tales about some elven gods when they talk about "dark wings " etc...
Also in DA2 she says "Perhaps I am a dragon."
We're still unsure about the true nature of those elven gods and where the hell they are.
Solas is a special case in the Pantheon , first in the old elven mosaic , he's shown as a wolf , all the others look like elf.
There's no vallaslin dedicated to him , no chant , no prayer.
Then Dalish tales says he walked among the Creators and the Forgotten Ones.
He also denies his Godhood , he says they weren't Gods .
Except well there's statue of him , and all the others were chanting the "We are Gods" tune.
And he's a god of "rebellion" , no tyrants would accept someone saying "be a rebelz it's cool" among their rank without cause.
So ...chances are he didn't started as a God , he was probably promoted as a demi god to appease the masses who were starting to question the divinity of their rulers.