1. Many "fans" are blowing their distaste for Halo 4 and Halo 5 way, way, WAY out of proportion. They're both great games with their own triumphs and failures; what game doesn't have those?
Your issue here is not realizing that people see the games differently than you do. I think Halo 4 and 5 have very few triumphs (I'd be hard pressed to think any triumph from Halo 4) and both have some very major failures. Naturally, I would say that my distaste is completely appropriate, but I guess you're the authority on that.
They feel more like natural progression while also expanding the skill-gap.
I guess I can see how somebody could see Spartan Abilities as a nonissue if they work under this misconception.
Classic Halo only had its artstyle due to graphical and engine limitations.
No single art is 'better' than another, they are purely subjective mediums.
FYI, "better" is a purely subjective term, that's kind of the point. Some art is, by subjective opinion, better than other. That's how art works.
Comparing and criticising them only gets you kicked out of an art gallery or museum.
I'm not sure what museums and art galleries you're visiting, but criticism is a pretty a fundamental part of the world of art. Some people will absolutely hate some art that others like, and you know, that's fine. Criticism is just the process of explaining the dislike (or like), and can be pretty valuable for understanding our own opinions, the art, and the opinions of others.