Not sure what is so depressing here. According to the chart, a total of nine listed networks died in 50+ years, this is actually astoundingly low.
And all IRC implementations are "interoperable" in the sense that a single client that implements the protocol can connect to any of them, this chart seems to be padding things a lot by calling every IRC server network a "chat service". A number of them also have or have had interconnects with each other in the past.
The depressing aspect is the accelerating fragmentation caused by more custom protocols entering the game. Supporting them all as the space grows will only get more cumbersome.
And all IRC implementations are "interoperable" in the sense that a single client that implements the protocol can connect to any of them, this chart seems to be padding things a lot by calling every IRC server network a "chat service". A number of them also have or have had interconnects with each other in the past.