I think it's a bit of both. For one, players are much better and there are far more resources and mods online that enable you to play better even if you lack skill. On the other hand there are things they implemented that unnecessarily make the game easier, but you might not recognize them as such... like quest tracker. After they added it as baseline I stopped questing. For some reason I felt disgusted and bored with it and for the longest time I couldn't figure out why, so I attributed it to boredom with the same ol' model and just skipped it for the most part. Then after staying away from it for years I was leveling another toon and then it hit me that the quest tracking was annoying me. Turned it off and my play experience improved dramatically, I had to read quests again, and search for things.
Some things that are quality of life improvements for some bother people who didn't need them. Some are just real, authentic improvements that were sorely needed. Some people just don't like change. Some people just like to complain about how they can't prove they are better than player x or y. There are a myriad of reasons that people feel the way they do about the changes to WoW, but in the end it comes down to one simple truth: You adapt or you die.
Adapt or move on.