Severin never really gets his due because, I think, of these reasons, and I think you could say the same about Mort Drucker, or even Jose Luis Garcia Lopez. He was dependable and regular and did lots and lots of work, and so his style became so easy to find that it becomes kind of invisible--defaults, in the mass mind, to generic. Think possibly of how you might have viewed Swan vs. Kirby in your mind as a kid and that might illustrate the tone I think Severin's work took on. Particularly after he started working at CRACKED. It's also that his work, while he was capable of exaggeration, still has a very old-fashioned(in the good sense) finished, almost too-solid illustrative patina that is so professional that sometimes it fools you; it doesn't occur to people that they're looking at something someone drew. He doesn't call attention to his style the way another equal-level craftsman--who is still thought of as very individual--like Aragones or Davis does. The latter of which really did become commercial art, but somehow never became seen that way. Consider that Severin, at CRACKED, would stuff panels full of stuff just like Elder or Wood. Except when he did it, it's more of a "meh" effect. This despite Elder having once been a collaborator of his. But in Elder's case, that's to do with his, you might call it, anti-style, which tries to de-emphasize its own personality and talk through another style. But Severin lacked that anarchic level of energy that leaps out of Elder.
It's like, he was looking at it as a kind of commercial art much of the time anyway. Part of that is, indeed, making the style an invisible tool to another end. So by his lights that was success.