I will generally agree with your assessment of Schumer as overrated and Rudolph underrated, but Amy Schumer is a stand-up and Maya Rudolph, as far as I know, has always been an improv comedian. Two very different skill sets. A lot of the people who've gotten Comedy Central shows, Key & Peele aside, have done it on the strength of their stand-up work: Jon Stewart, Dave Chappelle, Daniel Tosh, Nick Kroll and Anthony Jeselnik to name a few. I would say Carlos Mencia as well, but there seems to a dispute over whose stand-up work he built his career on.
I don't know the genesis of Inside Amy Schumer, but I imagine Comedy Central was looking to reach the female demographic and Schumer fit the bill of what they were looking for. She's done some good work with the show, of course, so I don't begrudge her success any. Her 12 Angry Men spoof, for example, was great (in my opinion). She's very Sarah Silverman-esque in that she talks openly and frankly about sex, and I can see how some people would see that as lazy, easy laughs comedy. That's true to a certain extent, but you can't build a career off that forever.