The main reason I've stopped using it is because others have stopped using it in favor of more modern alternatives. One hand clapping doesn't make much noise and gets a little boring.
It was designed for use from a command line. Various client apps have tried to put a happy GUI face on it but you still need to drop to the command line on occasion.
It's like trying to convince people to use Linux on the desktop. Experience shows that less than 2% will ultimately do it.
I still hang out in some channels but the ones I dropped out of were because everyone else dropped out of them. If there's no one to talk to then there's not much point to sticking around.