For me the most difficult thing with these awards is that I have no idea what's going on with other games I don't play. When I read the description of this award:
TF2 is the oldest game (by far) in this category. (Titan Quest was 2006 but the Anniversary Edition is 2016)
It might be true that devs for Warframe or PoE work a lot harder, but that's not the goal of this award when I read the description. The devs of TF2 still care about TF2 even after 10 years. The updates might not be the best, but they still care and they still want to improve TF2/make new content.
I'm not saying you shouldn't vote for the other games, because I have no idea what happens in the other games. But most of the arguments above are invalid or not relevant for the award itself.