ESO end-game content significantly encourages players to put together builds that pump out fast damage - which means that out of the 200+ total sets that the game boasts, we see a majority of players using some form of the 7 listed in the title (give or take a few that could be arguably be included - Morag Tong, Elegance, etc).
The issue with these high damage sets is not with the player base overvaluing them - it's with ZOS creating content that makes high damage sets almost exclusively the only way to play end-game content. We do not have much incentive to use many of the 200+ sets in the game - some of which could be really fun and interesting to use - because for most of us it's not worth significantly increasing the difficulty, for both ourselves and our teammates, by using a fun-but-weak set that hemorrhages DPS.
I'm optimistic that ZOS will be able to look at their numbers and see that most of their player population uses the same 7-15 sets while competing in end-game content, and make adjustments accordingly. It would be great to see an update which would give oomph to many unique and underused sets.
I think we can all agree that more set and build diversity - especially for end-game content - would be a welcomed benefit to the ESO experience.