I don’t really see it that way. It often feels very interactive to me, and the actions I take often depend on the reason I used it.
Obviously a Valkyrie used to get a pick is different than one used to escape and mitigate a Genji ult, or one used to get be able to help out a dps that is out of line of site or in a perilous spot, or one used to get off a sneaky res, or one used as a fight engage, or any one of the myriad other uses. And any Valkyrie usually involves some amount of dodging and repositioning.
But even the completely stereotypical fight engage Valkyrie has some decision making involved. Do you want to heal the main group? Damage boost them? What if there’s a secondary group? Sometimes it’s best to alternate between your tanks and keeping your widow alive, or damage boosting your McCree who is off to the side and about to high noon. Sometimes you want to do one of those things while taunting and dodging their long rage dps so you can take some fire off the group.
I agree that sometimes you end up doing just one thing, but often that’s not the case. And most Valkyries end up having more decision making than a Transcendence, or a sound barrier, or a nano, or a rally, or a amplification matrix, or even a coalescence. The only time it doesn’t is when your whole team is bunched up and taking damage, but those situations aren’t usually ideal for Mercy anyway.