I've seen it. I've also seen people talk down classical, disco and a few other genres at various points in my life. It seems there's always an uncool genre of the day. Which is a shame as people are simply limiting themselves.

Different eras of country music have different themes, values and styles, just like jazz and rock. That said, I heard some country music last weekend with a trap beat straight out of Outkast's Stankonia and it was... disconcerting.

disco, nu metal probably the two most hated genres

It's actually interesting to look at reviews of disco music on RateYourMusic going past the last decade. You might notice a pattern of the older reviews criticizing it as vapid and cheesy, while the newer reviews praise it as danceable and fun.

I think we're finally brushing off the excessive dismissal of the form, probably in no small part to the rock-worshipping generations being drowned out by the newer generations that have no such allegiances.

There are many repetitive lyrical themes that seem to be associated with particular genres, and personal preferences associated thereof. I feel like country used to have more variety- my father used to listened to it- but it's kind of coalesced into "I drank a bottle of whiskey and cried in my pickup truck when you left me" which isn't really my thing. Whereas I'm kind of ok with every power metal song being some variation of "fire! dragons! swords!". The things that aren't really stand out though, such as Kamelot's concept albums Epica and The Black Halo, which are based on Faust. There's also Van Canto which is a rather impressive German a capella power metal band (with a live drummer). In general, power metal seems to be more self-aware of how ridiculous and repetitive it is. See Gloryhammer, which is effectively a power metal parody band, taking the lyrical absurdity up a notch and replacing dragons with unicorns etc.

If there's any self-referential/parody country music out there I'd actually be curious to hear to it.