That's a little too simplistic and I know you're smart enough to know that.
Generally speaking members of a conference are essentially similar. Similar in facilities. Similar in the academic realm. Financial committment. And similar in their appeal to prospective players/coaches. When you are competing with other programs that are more or less the "same" then it IS difficult whether you are in the valley, the summit league or the Big 10. You have to do what you do better than the others you are competing against. But there are also inherant advantages/disagvantages when you are talking about competing outside your conference. Recruiting to a Big 10 school, be it Nebraska or Michigan State is always going to be easier than recruiting to Wichita State. So Big 10 teams SHOULD be better.
Saying it's tougher for Nebraska to compete in the Big 10 than it is for a Creighton to compete in the MVC isn't looking at the big picture. Creighton doesn't have a conference network where it can tell recruits that they'll be on TV every game. They don't play in a league that the top HS recruits want to play in, given the chance. They don't have national recognition like Nebraska does. Being a "football school" isn't, or SHOULDN't, be a disadvantage. It's a huge advantage as far as campus life goes and "branding". The list goes on.
One other big advantage is that nebraska doesn't need to be great to make the dance. They just need to be pretty good. Look at Purdue, Northwestern and Illinois. These are wildly mediocre teams WITHIN their conference. And they are still regarded as "bubble teams". CU, Wichita State, etc. don't have the "power conference" affiliation that gets them the benefit of the doubt. They need to schedule as tough as they can but that's difficult given the nature of College BB scheduling. So they need to go out and win 27 games and can't afford more than 1 or 2 bad losses. In a power conference you get countless opportunities to get that "signature win".
So would it be tougher for a Creighton to walk in to the Big 10 NEXT year and compete? Hell yes. They wouldn't win it. They sure as hell wouldn't finish last or even in the bottom 1/3 either. They would still be a tourney team if they were in the Big 10 this year. No doubt. Now, over time...with the opportunity to recruit to the Big 10, the TV exposure, the additional money, the sparkling new practice facility they could afford to build, they'd have every chance to compete in that conference. Would they? Depends on the man in charge. NU has all those things now. They need to get a man in charge that can lead them to competitiveness. Hell, nobody even remotely expects NU to replace Mich State as the class of the Big 10.