Al, I have absolutely no idea who you are talking about, but certainly a quick look at my own festival lineup this year makes it abundantly clear that it's not me. My own definition of folk is a pretty broad church, and there are myriad artists and bands on our bill who don't fit the 1954 definition, or that you wouldn't find on the "dusty shelves of Cecil Sharp House". Don't believe me? google Genticorum, The Spooky Men, Mr B the Gentleman Rhymer, Alasdair Roberts, The Yiddish Twist Orchestra, Moishe's Bagel, Nidi d'Arac, Peter Bellamy's The Transports, The Old Dance School, Ethno in Transit...I could go on. We have a Motown ceilidh and a silent disco, for heaven's sake - I don't really think we're treading any purist line.
The word folk is little more than a marketing tool and a record industry genre these days, and I'm not particularly precious about it. "Traditional" is another matter - but there's no reason why it shouldn't be.
I suspect, as I have suggested in the past, that you simply mean that you, and certain of your friends, don't get as many bookings as you would like. If you wish to see a conspiracy in that, I'm not going to stop you and neither will anyone else, I suspect. But that has precious little to do with Mumford & Sons, who are doing very well for themselves.
You can't MAKE people like what you like, Al. If you think it's that great and isn't getting the platform it deserves, start your own festival or regular folk event. Programme everyone you think has been hard done by. If you sell enough tickets, you'll have proved your point, and given them the career boost you think they deserve. If you don't...well, that's the risk we all take, isn't it?