And those things depend upon your teammates carrying their weight in the first place.
Getting value out of Damage Boost depends upon your teammate(s) dealing a respectable amount of damage. If they’re not doing that, the value of Damage Boost is entirely null.
Getting value out of Resurrect depends upon whether or not your dead teammate’s positioning was good in the first place… and… well… The reason bad positioning is considered “bad” and good positioning is considered “good” is that that the former is more likely to end up in your death than the latter. So if someone on your team dies, there’s a good chance their positioning isn’t suitable for Resurrect. In such case, the value of Resurrect is entirely null.
The one grey area here is “saving a teammate”, but in such case, the other main healers (and even the off-healers in some cases) still hold a strong advantage in player agency there. 55 HPS can only hold up against so much. Meanwhile, every other main healer has at the very least the option to “go nuclear” on keeping a teammate alive, at least for the moment. Baptiste has Immortality Field and/or his Amplification Matrix to dish out 156 healing/second (not including Regenerative Burst) or to swiftly kill the enemies attacking the ally he’s trying to save. Ana can deal over 200 healing in under a second with just her Biotic Grenade and a single shot from her rifle (not to mention followup shots dealing more than 100 healing each), and she can potentially Sleep one of the enemies closing in on the ally she’s trying to save. After all of that, she still has Nano-Boost. Moira can temporarily ramp her healing output up to 135 HPS using her Biotic Orb and primary fire, or up to 205 HPS when combining her Biotic Orb with her ultimate.
Off-Supports, on the other hand, often have other ways to save teammates that don’t depend upon raw sustain. Brigitte can directly engage the enemy, which increases the sustain of her ally, sure, but more importantly, it prevents the enemy from finishing the kill. Zenyatta can slap an Orb of Harmony on the ally, but that’s not where his main clutch-save capacity comes from. He can dink the enemy a few times and they’re no longer a threat.
With other supports, you have ways to increase your saving capacity through your own direct actions. You have “nuclear” sustain options that you can use as main healers, and you have alternative methods to protect your teammate as off-supports. Landing a well-timed Biotic Grenade as Ana to save a teammate? That’s player agency. Your own actions led to you having that ability ready right then, you got the projectile arc right, and you timed the grenade right so that it wouldn’t be blocked by the enemy. You’re rewarded with a teammate that is not dead. Mercy, on the other hand… You get 55 HPS. That’s it. No ways to increase their chances of survival through skill expression. Just 55 HPS. Good luck.
Of course those things can happen without me. Put another support in my position and you could get much different results. The results there would actually vary within a given hero based upon the player’s skill, because those supports actually have agency in that regard.
Put a Platinum Mercy in my position, and you have the same saving potential. I’m not exaggerating.
Every support has unique abilities. That’s not relevant. What’s relevant is how much the value of those abilities depend upon the player’s own decisions and skills.
That’s like saying “If you don’t like the policies present in the United States, move to a different country.” I’m not fond of other countries. I prefer where I am now. That doesn’t stop me from learning from the good aspects of those countries and seeking to apply them to the place I actually care about. That’s not entitlement; that’s common sense.