It just had Ivy, Riddler and Catwoman as background characters and they fleshed out only Penguin. Nothing wrong with that. Penguin might the only season 1 final boss that Gordon goes against.
Yeah, but that was on top of introducing Falcone, Fish, Gordon's partner, a pair of good cops with wrong suspicions, suspicious wife, and more than a couple of hints at the Joker, (without it being the actual Joker) all as potential obstacles/antagonists.
It was a lot to cram into one episode. Personally I prefer it when they do that straight up and then allow the show to develop afterwards even if the first episode feels a little off pace because of it.
As long as they don't just keep giving them all cameos just to remind us they're there and not do anything with them. If there's a purpose to it then I'll be happy.