Paul is determined to become a world champion as a professional boxer and is even targeting a showdown against Canelo Alvarez.
While he is undefeated in his five fights, he is yet to fight an actual boxer with four of his five wins being over ex-MMA fighters, including Tyron Woodley.
The YouTuber was expected to face Tommy Fury last year only for the half-brother of Tyson Fury to pull out due to injury and illness.
When asked on Paul's chances of winning a world title, Hearn said: "Everyone's entitled to have a dream, [but] I think there's absolutely no way he can beat a world champion and become world champion.
"But I will say he's improving a lot, he's dedicated to the sport. I don't know how good he is because he hasn't really faced a real fighter yet. It's not his fault, he signed to fight Tommy Fury..."
Paul interrupted and replied: "A five-time world champion in Tyron Woodley is a real fighter."
Hearn then responded: "Mate, he's not a real boxer. He's not Jake. A real boxer is someone that that is his craft.
"What I'm saying is, [Woodley] does not qualify to give you any right to talk about fighting for a world title - and nor does Tommy Fury actually.
"But, I'll give you the props, I'll give you the respect, you're improving all the time, but the proof will be in the pudding.
"By the way, I have said that I think Jake Paul is better than some fighters. But I don't believe you will ever get close to being a world-class fighter."