Everything seems blown out of proportion, in typical fashion.
IMO, Splatoon is hardly lacking content, and certainly not to the degree people are asserting. The game is trying to pull of something that needs a decent community to be accomplished. Until that happens, certain measures are in place. What's there, however, is more than adequate. New maps - which would have been rolled out later, regardless - are a given. Some of those said maps were actually seen before, which suggest this is more about a strategic rollout, than a desperate attempt to patch things post-launch. A simple option for team battles - which doesn't require any unique mechanics, infrastructure, maps etc - doesn't seem to scream "unfinished game," but seems more about Nintendo wanting the community to grow a bit before certain online squads begin to reek havoc on everyone else. Did Nintendo made the right choices? Who knows, but this is certainly a unique situation to be in, and I understand what they are trying to do.
My point is, Nintendo realizes this game needs a proper community to thrive, and for the time being they believe they have to exercise some control. I think there's plenty content there until things really get going. However, reviewers should review the game as is. That can be bad for Splatoon if some reviewers get overly hung up on "but but lacking content till August," but it's fair, and we need not make altering scores a habit! They may get early access to ranked battles. Other than that, a few new maps and a couple match-making options doesn't/shouldn't dramatically affect the game's core appeal, like we have seen with some other games recently. Just fairly & honestly rate what is there. Update impression later if necessary, but leave the initial review score intact.