This sounds like it’s coming from someone who never plays support. There’s a typical expectation that kind of person has for supports: they’ll always be available to heal me no matter where i am and what is happening; if my hp is dropping, someone better be healing it already. But those expectations are unrealistic, and you only realize that when you play support.
Fun fact: A lot of the time they’re struggling to get line of sight on a critically injured teammate, and by the time they finally do, the teammate dies. Not only that but now you’ve technically wasted time getting to them, and could have been healing someone else, and now They’re injured; and while you’re healing them, someone else dies. That happens ALL THE TIME, and there’s very little you can do about it.
You have to accept the fact that a healer can’t be healing everyone all the time. There are gaps. There are situational changes, there is line of sight, there is point of view (you don’t have 2 eyes at the back of your head) there is incoming danger forcing you to run one direction over another and ditching one or more teammates in the process, there’s all kinds of situations. And yes, sometimes you have to judge that it’s better to dps at a particular moment in time instead of healing. A lucio booping off 2 people is a lot more advantageous than healing his teammates who are going to take longer to kill those 2 ppl (and possibly die in the meantime). A mercy pulling out her pistol to finish off a turret or anything really can be a lot more advantageous than not doing that, if the situation calls for it and you pull it off in the interest of time.
You people make it seem like there are supports out there who literally only dps. They have 0 healing done, and they always ignore their teammates so they could just dps. Really? I have seen exactly 0 people like that.