It's not that I hate 3d effects, but I'll avoid them if I can, for a variety of reasons.

As other people have said - I wear glasses, I having to put the glasses over my own glasses just makes it difficult. They don't stay on and I have to hold them, it makes the image askew, it's uncomfortable on my nose and ears when it does "fit". They really should come up with a more inclusive way to watch these as a good portion of the population wears glasses.

For another, I suffer from migraines and 3d effects not done well tend to trigger them, and I already have enough triggers that I can't avoid.

A strange one needs a little bit of backstory - I was never great a sports as a kid, could never quite catch a pop-up or hit a fast ball, but I was great at throwing or other aspects. People wrote it off as just "unathletic" and I went on to live my life as a weird nerdy kid despite the rest of my family being athletic. Fast forward to my adult life when I was put on a very strong medication and needed a very thorough eye exam and a result to set a baseline to make sure the medication doesn't end up damaging my retinas (thorough to the point that the exam was 5 hours and I had tests done I'd never seen it heard of before).
It turns out my eyes/brain only interpret half the depth perception of the average person. So what I'm seeing during a 3d movie is not what's meant to be seen. And since this is not an eye exam that would be regularly given - who knows if it people that are complaining about the movies have the same issue I do? Cartoon-y 3d (like Disney world/theme Park things) is fine for me, but things like Avatar just give me migraines.