Eric

Aidan we were told very early on they do not have Conquerors Haki, that is why they had such powerful devil fruits. We know this because we were told the only Marines with Conquerors Haki were Garp and Sengoku l. We also know Garp is the strongest Marine despite only being a Vice Admiral.

Uh dude has no Conquerors Haki. He's not standing up to anyone. He tanked a hit from a guy who was already dead. White Beard was only living through his sheer willpower alone, trying to say that surviving fighting him as anything more than you got lucky is a joke.

All that and he can't even stop a former Warlord. He would absolutely get bodied by Kaido or Big Mom. Shanks wouldn't even need to try hard to destroy him. You ignore the key factor of his complete and total lack of conquerors Haki, which is the be all end all at this point in the saga.

Dragon's fruit could potentially be either of those, it could also be something along the lines of Mythical Zoan Devil Fruit Thunderbird. Mythical creature capable of controlling the weather/storms.