Well, at the least, the action/fight scenes are more "action-y" because of the nature of anime/video. I think at some level, all popular manga/anime
need to pander to their audiences. Once a series gets popular, then character polls run in the manga magazine start to decide who a character ends up with or who gets focused on more.
When a series gets popular, then the publisher usually will get more say in what happens, and if it gets really popular, the publisher can make the mangaka continue it far past the point where the mangaka has lost interest in the story (I kind of feel sorry for the person who writes Naruto), of course, back when YYH was being written, most manga didn't go past a certain number of volumes, which is why there's speculation that Togashi was pressured into ending YYH early by Shounen Jump/Shueisha....
As for animation quality, which you mentioned, it probably has something to do with a crazy world of
tight anime deadlines.
I could go on about the
dark side of manga industry, but I guess I'll just say that with anime/manga, as with most things that are bought and sold, what makes money and what doesn't is a major factor in what gets published...I was pretty disillusioned for a while after I began to see obvious signs of pandering to fans in anime/manga, and avoided it for a short while, but in the end, I still think anime and manga are great mediums for storytelling and I enjoy them both for what they are...Sorry, I got off topic, I guess my point is that I can't completely avoid fan pandering, but I still find things to enjoy in the YYH anime, and it's OK if you don't like the anime as much as you did, it's fine to just enjoy the manga.