Tl;dr: Too many heroes lost their niche due reworks or balance changes. It is killing their individuality and unique qualities that made them what they were. Instead heroes are getting pushed slowly and slowly to become the same as one another until every hero will be practically interchangeable.
Reaper’s recent changes are forcing him to be a squishy targeting flanker. Every other single flanker already does that job but better! Tracer, Sombra, Echo, and Genji all can flank and target squishes. Reaper was the one flanker that was good for targeting tanks, and now he isnt. So instead of them trying to rework him to fill into a role already massively overcrowded, let him have his niche!
Hanzo lost an unique ability unlike any other in the game that could kill using map geometry. Did it suck to die to, sure. But it was much more easy to outplay. All one had to do was evade it once and you wouldnt have to worry about it. Now he has a better version of McCree fan the hammer, which is now why Winston (A character originally made to counter snipers) gets streaded by Hanzo.
Symmetra’s rework was the worst offender of all. She lost her niche of being the only non healing support and the only hero with 2 ultimates. 2! Now she is a character that gets overshadowed in a category of heroes that she doesnt belong with.
DVa was one of the best Tanks at counter hitscans especially when high ground was involved. She could outplay so much with great DM play. Now she gets streaded and is probably the worse off tank in the game.
Bastion was better with the less spread and ability to headshot with his sentry mode and that was what made him who he was - an character with next to no mobility but insane, unmatched Raw DPS. Instead they gave recon mode some buffs at the expense of sentry mode.
Brig was supposed to be the first Healer/Tank hybrid. I’ll admit she did too much. He burst damage and tankyness were too high. But they reworked her in the wrong way. They buffed her healing, gave more packs, and essentially made her just another Heal bot; while at the same time taking away pretty much all her tanking and burst dps away. They should’ve keep her most of her tankyness while nerfing her burst dps.
Please for the love of God, stop forcing changes that kill everything we originally loved about the heroes. Stop generalizing them! Stop forcing heroes into roles they shouldn’t be in, roles that are already filled! STOP IT!
EDIT: Mercy was another hero who lost her identity. While I’m glad she at least still has rez to some capacity, those big moments of resurrecting an entire team is no more. Now she has a much less fun ultimate ability in my opinion (and many others based on this thread). Instead of making game changing impact with mass rez, she gets to play around and buff/heal her team.