Definitely, when the situation is clear cut the shot caller or the most helpful should get the honor.
But that's the thing, it's not always easy to judge. Fun, yes. Easy, no.
Sometimes it might take one good support early game for the adc to go 2-0 and snowball, get kills on their own, but no one will ever know how it started, and in the end they will honor the adc. And yet I don't think they are wrong, because first, it's a skill (that I don't have yet) to use a lead, and second, it is a skill to stay alive without a babysitter (be that any other team mate, not just support) as an adc.
And as someone else suggested, the older system was preferred where you could honor the entire team. This is a team game after all and if some games are won because of team spirit, then everyone deserves an honor. We're here to complement the rest of the team, why not compliment the rest of the team, as well?