Humans aren't that bad.
I think people haven't had a chance to get a grip on some of the game mechanics. I know one of my friends was going on about how good Darkvision was, and then I showed him you could fire dip your bow and then shoot all of the hanging braziers around the chapel and just light up the room before the encounter starts.
Not to mention turning on candles, lighting torches, ect.
Humans get twice the stats as anyone else, and as such can dump and redistribute those stats to get very valuable third priority stats.
A good example is a Light Cleric who wants to go STR weapons, needs some CON and WIS, but can still achieve a respectable DEX for AC (Really good with Light Domain Reaction) and more importantly initiative which can really make a huge difference in encounters.
The next time you fight a particularly difficult encounter reload and initiate combat a few times until majority of your party throws out some good initiative rolls and see for yourself how much easier the encounter becomes.
Yep, their main feature is supposed to be flexibility. It's not like you need min-max to beat this circus anyway.