When I began investigating classical music about seven years ago after 25 years of blues, jazz and rock, I plunged magpie like into orchestral, chamber and instrumental repertoire but had this problem with the operatic voice ( for want of a better term ).
Interesting topic, Mr. Z. It could almost be me writing the above statement!
I still struggle with the "operatic voice", and though I'm starting to appreciate opera more, my general opinion is "nice music, shame they had to have singing in it
I do like music for chorus rather than for solo voice. I also found I like older vocal music (baroque or earlier) more than recent (18th-19th centruy) vocal music. And finally I isolated the problem I have with the "operatic voice" -- it's the "warble" factor, or excessive vibrato that puts me off. I prefer the more "pure" tones of older-style singing. (Apologies if I'm not using the correct technical terms; I hope people understand what I'm trying to say.)
Incidentally I find the same is true of modern (pop) singers. I much prefer voices that hold a pure note over those who warble all over the place. Sadly, warbling is the "in" thing these days.