I was around the MMO scene back when Blizzard was developing WoW, and this was the general sentiment around the community even at the time, it was seen as the care-bearest of the all the care-bear MMOs (which is what people at the time called MMOs that weren't hardcore enough for them, particularly in the PvP area). A lot of people that WoW was a step backwards for MMORPGs. At the time MMO developers were doing a lot of interesting things with games like DAoC, Star Wars: Galaxies, Anarchy Online, etc. There was something for all tastes, in particular games like SWG were starting to feature persistent player-build towns, non-combat focused professions that actually made sense to use, interesting skill systems and a more social experience.
At the time WoW felt like a return to the old days of Everquest, only even more simplified and polished (which makes sense since some of the same people were involved). There was even a sort of a competition (more of a shouting match) between Everquest II fans and WoW fans before either game got released as to which would be the future of MMO games. We all know how that fight went.
What I and many MMO fans at the time failed to understand is that WoW wasn't for us. It was for people who had never player a MMO game before. It wasn't an attempt to get MMO fans invested in Warcraft, it was a brilliant move to introduce all the Warcraft fans to MMOs (and the marketing material at the time was very clear about it). It was all designed from the ground up for people who had never even known that MMOs existed, since the MMO market was pretty small back then, and what little there was was pretty divided.
This is also why many people these days have fondness for "Classic WoW," because it was their first, and you never forget your first. Incidentally my first was a pretty shit game called The 4th Coming and I still remember it fondly, while ignoring most of its faults (what kind of casual needs an interactive map anyway, just look at this still picture that roughly resembles the world and navigate using landmarks, much more immersive that way). This is also the reason why all the WoW clones never caught on. The people making them (or changing their game to be more like WoW, looking at you New Game Experience) failed to realize that most WoW players don't really like MMOs, they like WoW, specifically.
Writing this has made me feel pretty old, but I very clearly remember scoffing at WoW players as casuals and their game as an Everquest clone. Here I was playing much better games like UO and SWG and they didn't even know better. Well, time passed and now I'm the one that didn't know better, but I'm still kinda bitter that the success of WoW massively contributed to the death of the type of MMO I liked, and even if it looks like WoWs influence over the newer MMOs is slowly fading, I don't think I'll ever get to enjoy any new MMO the same way I enjoyed the originals.