Certainly classes are more similar. Well, at least we say they are. Is a frost bolt all that different from a shadow bolt? Was it ever? Those who complain about homogenization need to confront a troubling fact: it happened long before WotLK, before BC, before WoW even existed. When have there not been ranged physical, melee, and casters? Ultimately people are throwing around similar spells except for graphics and secondary effects. Or, I hate to use it, but let's look at real life. Look at how homogeneous bullets are: explosive in the back propels little piece of shaped metal into person. Why ever use different bullets?
A lot of everything is a lot like everything else.
Pardon the wording in this paragraph, but it's going to sound strange. Let's take warriors and paladins in vanilla (and ignore unpleasant details such as dresses). They're generally melee damage with plate and can also use shields and tank. There are only two major differences: heals and playstyle. Let's fast forward a few years to now. What's different? Well, they're a lot more similar now. They have strikes and AP buffs and a whole lot of damage and tanking and in many aspects are interchangeable. And yet, they're as different as they ever were. They still have a different feel. Despite JotW, mana is not rage. Play them both and you are lying or delusional if you think they feel the same. They have the same two-handed weapons as always, but they are still different, as they always were.
In other words: Classes always had overlap and that overlap hasn't changed much.
Now let's look at freedom. You are more free than you ever were in WoW. Why? Because we no longer need any given class (except priests on Raz). So how does that make us free? Here's how: play whatever class you want and it can do what you want to do (well, obviously priests won't be doing much tanking, but you get the idea). Or reverse that, pick a role and then pick your class. Want to tank? Great news, you're not stuck with only a warrior.
On the subject of warriors: why play one anymore now that three other classes can tank? Because you want to. Let's look at that again. You previously might play a warrior because you wanted to tank, and so you didn't actually want to play a warrior. Now though, you will play a warrior because you want to play a warrior. How is that not an improvement?
Call it homogenization, I call it nothing changing except greater freedom.
 This isn't to say that homogenization isn't a concern. It is. But the homogenization argument is usually used too hastily, probably by those who are afraid of being players rather than classes.
[edit a day later...] This is an interesting and relevant post by GC.
We want you to get a spot because you know what the blank you're doing, not because your class is programmed to always do top dps or inflate raid dps through a miraculous spell that you impart by clicking a button every 30 min.