the queen of prog?

That's an interesting point. It seems to me that apart from a diversity in the voices that were widely popular in the 60s/70s, there's a common style and sound to the popular vocals that I can't quite place a finger on. A bit of rawness in comparison to now, certainly. The overriding trend of the 21st century in mainstream vocals has been towards a particular brand of polished 'perfection' or over-perfection in vocals, even aside from autotune and the like, a very particular sound that's very precisely mannered, polished and smooth, with the Mariah Carey-esque embellishments, all of which ties in to the quest for polished over-perfection in music and mixing in general. It even extends outside of the mainstream to rock and prog (to me, there are plenty of modern prog singers that exhibit this sound, though certainly to a lesser degree), and even in jazz, Buble & Harry Connick Jr exhibit this kind of sound in comparison to Sinatra, for example.

Of course, it's not all like that- especially the main rival, the indie mumbly vocal, and there's plenty of other stuff, especially as you branch out from the mainstream. But it's certainly the prevalent style, in comparison to the prevalent 60s/70s vocal sound.

Now, in a bid to tie this back into the actual subject of the thread, a friend of mine once commented that she didn't like female vocals, because they 'all sounded the same.' I wonder if this is because female singers are far more common in pop and so on and nearly absent from many other genres, whereas males are common across the board- so the majority of female singers heard, being pop, will fit the polished style, whereas there'll be plenty of men in other, especially harder genres that deviate from it.

The other sweeping trend is in the delivery of the words itself in a very flat and flavourless (but polished and flawless) accent.  This is across the board.  It's the same in my country.  Either artists have forgotten the importance of cultural nuances in endearing their work to the audience and giving it personality or they do it because they are afraid of how the audience would react.  In the 70s, you had such a wide variety of English accents.  Lake almost seemed to imitate American accents.  Gabriel was very English. So was Jon Anderson but he brought a different accent and likewise Ian Anderson.  Ozzy sounded absolutely nothing like Gillan.  These folks were all experimenting and trying to arrive at what each perhaps thought would be the perfect vocal style.  Over a period of time, it seems as if artists have already made up their mind about what would be a perfect style and just reproduce it.  Many of them with assembly line uniformity.   You have an interesting point that maybe with so many female singers in pop, this uniformity breeds a general dislike of female singers.  A parallel I can immediately think of is women's tennis.  They all seem to play from the same coaching manual.  Well, not all, but only discerning fans today would be aware of which ones play differently whereas earlier the difference between Graf, Pierce, Sanchez-Vicario, Hingis was more readily apparent.  

Another point is time tends to cast a shroud over unremarkable artists or unremarkable works of art and spotlights the more unique ones for future generations.  Maybe our time will look very different with the benefit of hindsight, it's hard to tell.  I remember sampling non-Carpenters versions of Won't Last A Day Without You.  Man, they sounded annoyingly uniform and I could totally see why the Carpenters cover has stood the test of time.  

But something has changed about just the way vocals are treated in the studio with a result that is not particularly agreeable to my taste.  Often times, the vocals sound better in the live performance of the same track so I wonder if it's just over compression, cutting out the subtle dynamic variations that make a performance lively and human.

My favorite grumpy is my ultimate favorite fabulous awesome one! True this!