IRC is not simple. Simple if you want to write a bot for a specific channel on a specific server, I suppose; but infuriatingly difficult to write a client for.

The curse of IRC: no standardization. There have been two major attempts to define a standardized version of IRC, neither of which has been successful, and neither of which are entirely adequate.

There are literally hundreds of messages, a large number of which are server-specific, and no two servers work remotely the same.

The protocol is also painfully bound to terminal-style user interfaces. Wrapping a clean graphical user interface around the protocol is difficult if not impossible. And any attempt to do so will require extensive customization for each server variant that the UI intends to support. And anything less than a clean wrap produces a user-interface that demands a sort of computer literacy that ordinary and casual users should not be expected to have.

Character set support is also fascinatingly and tragically broken. The ACTUAL official standard character set: Western European, with DEL replaced with an additional character to support Norwegian users. In practice choice of character set is cultural and varies from server to server, and from channel to channel. Some use Western European character codings, others use local or national codepages, many (but far from all) use UNICODE.