This pithy statement after spending a paragraph complaining about tanks belies the reality of the current state of Overwatch.
DPS isn’t just “killing,” it’s knowing who to focus and when, being able to land shots when it counts and confirm kills for your teammates, winning enough 1v1s and getting picks to make teamfights in your team’s favor, using cover wisely and avoiding getting picked off to make the enemy team’s push more difficult, knowing when to make the risky play and trade your life for 2-3 picks, baiting cooldowns for your tank to win the tank duel…
Support (besides Mercy) arguably is most of that, plus keeping your team alive, but also knowing when to heal versus when to get some damage in. How good is your tank, do you need to babysit them, can you balance giving some resources to your DPS, etc.
“Tank diff” is often just a convenient scapegoat for 4 players (80% of the team) to band together and blame their poor gameplay on one player, giving them the democratic majority. It’s not a tank diff if the DPS are frontlining and getting picked first every fight, then finish with 15+ deaths in a 2 round game. It’s not a tank diff in S9 if the tank’s supports are healbotting while enemy Moira and Illari wreck havok on the backline.