Do you think that Bitcoin has become too slow to compete with the relatively quick alt coins out there?
I thought you are addressing the slowness of its confirmation with transaction. Why are you looking for competition? Its clear that no one can be matched with bitcoin.
Is it realty competitive to have a slow community rather than a centralised decision making in development?
I don't know in what aspect you are looking with a "really" competitive slow community.

In other words, does the community effect of decentralisation enough to counterbalance the difficult decision making processes?
The community does portray a big effect about decentralization. And decision making is depending on everyone's perspective but not as a whole.