Lizzie, I haven't noticed anyone "trashing" Loreena Mckennitt's music. All they've said is that they don't like it, which is quite different.

I listened to one of the links you gave, the mummers song. It struck me as well-performed but I found it uninteresting. Like much modern commercial music, it makes a nice sound but places no demands on the listener. She has a pleasant voice but one without much individual character, and the words were largely inaudible (although I concede that YouTube isn't the ideal listening environment) so I have no idea what she was actually singing about. The instrumental lineup offered scope for something really interesting which never materialised. And was she really playing that accordion? Her fingers didn't seem to move.

There's nothing wrong with liking this stuff, or Enya or Clannad, or any other modern commercial music for that matter. Personally, I find it bland and uninteresting, but I can't deny that it's commercially successful. I don't think it has anything to do with "Celtic" music, but that's a branding issue, or with folk music and I don't really think it has a place on this forum. But that's not to say it isn't good music or that I'm somehow morally superior for preferring something with a bit more substance.