If Ridgeway can just be serviceable, that'd be a nice win. There are people that would say hey, we really addressed DT this offseason wtih Ridgeway, as if he's some sort of Aaron Donald clone. LOL.
What we're looking for in Ridgeway is someone who can hold the point of attack against double-teams against the run. You can find players like that later in the draft. If you want an Aaron Donald, you either need to draft him in the first round or hope you get lucky with players like Trysten Hill and Osa Odighizuwa.
Stud NTs are far easier to find than stud 3-techs. Now, if you want an NT that can stuff the run and put pressure on the passer, then you need to look early for those as well. I would love to see us do that, but that doesn't mean Ridgeway can't address that two-down NT role and even possibly be more than serviceable in that limited role. Not saying he will be, just saying what we are expecting of him is a whole lot different than what we'd expect from a player like Donald.