They're not treated fairly.
They are or they used to be a complex class that rewarded tactful gameplay and clever ability usage. Something that not a lot of people can do or enjoy. So when something comes along that actually requires a shred of thought that stomps you the brainless power/condi burst combo player and you can't kill something, you start ranting and complaining on the forums instead of realizing this entire time that you have CC breaks, condi-cleanse, and other utilities integrated into your class that could solve literally all your problems. Or you could just use common sense and go fight something else instead of expecting to kill everything. It's the same fallacy of "why can't I kill bunkers". Bunkers can't kill you, use your kitten head.
People are idiots and I assume there are very few if at all Mesmer mains on the Anet balance team let alone in the studio. If there are, they need to speak up.