While your point is not without merit, you're saying it like we haven't had multiple opportunities and last year's Tournament performance was anything other than the exception. While the Big Ten's lack of titles needs to be explained in some way and this is as good of a theory as any, the way you say it indicates we haven't had teams talented enough to win the NC. When you place nearly HALF of the conference in the National Title game since 2000, there is plenty of talent in the conference, and it's not as if these were all blowouts. We easily could have won multiple games in this timespan with a couple different bounces of the ball:
2002: Maryland over Indiana, 64-52 ... can we count this now??
Not particularly close, though.
2005: North Carolina over Illinois, 75-70 ... game went down to garbage time free throws, and ILL played the final 8 minutes without its starting center to defend Shaun May.
2007: Florida over Ohio State, 84-75 ... that OSU team wins the title the year after, IMO ... just ran into a once-in-a-generation Florida squad.
2009: North Carolina over Michigan State, 89-72 ... UNC was probably more talented, but that was a damn good MSU team.
2013: Louisville over Michigan, 82-76 ... game went down to the wire.
2015: Duke over Wisconsin, 68-63 ... another game even close than the score indicates.
2018: Villanova over Michigan, 79-62 ... probably the best case of your point being true, IMO.
Again, I agree with you that the league needs more NBA talent and that this is part of the reason we haven't broken through since 2000. However, there have very clearly been multiple Big Ten teams "good enough" to theoretically win it all; it's not like last year is the norm, where tons of teams are getting bounced in the First and Second Rounds. This list doesn't even look at great Big Ten teams that didn't make the title game but were good enough to ... March Madness is a lot of luck, and that (along with your point) is part of the reason we haven't won it all in so long.