I think this is an important factor since several decades. Almost everyone in the western world has grown up with "microphone crooning" since the 1950s or so.Like many CM enthusiasts, I did not like opera (actually, classical singing in general) when I first started listening simply because I wasn't used to the style of singing.
As for the question in the title, I do not think that most lovers of classical music do not like opera. There is, however, some sorting into opera lovers who love opera much more than most other music (and they tend to congregate in separate fora or subfora) and those who prefer non-operatic classical music. But I think the subgroup who doesn't like opera at all is rather small.
To be fair, Les contes d'Hoffmann does not belong to any of the three categories you mentioned before and it is almost post-modern besides maybe also ridiculous.I can't get into most bel canto, verismo, and Baroque opera (with some exceptions) because not only is the music often repetitive, I find the plots to be contrived. I tried listening to Tales of Hoffmann the other day and just couldn't get past the ridiculous stuff I had to accept in order to enjoy it.
I like opera but I don't like it so much on recordings and I am too lazy/too poor to attend it frequently in the theatre, so I don't listen a lot to opera in the last years. And there are lots of operas I don't much care for and some opera fans (especially those obsessed with singers) are a bit ridiculous, so I would also understand people not being keen on some typical online opera discussions, despite liking the art form.