Sivran writes: "Thus, blame B5's bad 5th season on UPN."
But who do I blame for the lame ending of the Shadow War in Season 4?
If that was JMS's intent from the beginning, then bad, bad JMS! If he changed it to fit into Season 4, then bad on him again.
I discovered the show early in Season 3, and subsequently caught most of the early episodes in reruns. I got the impression there was a decent 3-season story hiding somewhere in those 5 seasons. Perhaps with a faster pace (three seasons) the ratings would have justified a "Bab 5 Reloaded" series at the end of the first, e.g. to cover the telepath war.