Among other things, moving images cause problems for me. Depending on size, placement, number it may “simply” be that I’m unable to read the surrounding text, or it may cause nausea and dizzyness, etc. Multiple images which change on mouseover are also disorientating, although I tend to keyboard where possible, which helps to cut down on that problem. 
Depends on your perspective whether I’m “cutting out a very large portion of the internet”, or whether a large portion of the internet is excluding me. 
As I said, I will enable JS where I feel there’s a good reason, and provided that it has no adverse effects (for me) along the way. I use NoScript, so I can allow some scripts and not others, if I so choose. But it’s a pain to have to go through that palaver.
Discourse uses JavaScript extensively, and I initially found some aspects pretty hard to live with. However, both Discourse and the SitePoint team have made fairly small changes which have made a big difference from my point of view. I’m happy to enable JS where I can - it’s just that so often, I can’t. 
Yes, I think that’s what the problem boils down to. You only have to look around the forums to find people advocating more videos, more slideshows/carousels, more “Web 2.0” features (whatever that means), generally more bells and whistles. Usability and accessibility no longer seem to matter in many quarters. And it’s because of the bells and whistles brigade that I - and others with similar issues - have learnt to habitually disable JS.