The 5th season of B5 would've been much better if UPN hadn't given jms the run-around. When it appeared to jms that B5 would be cancelled after the 4th season, he stuffed 5th season stuff into the 4th season, so the show could have some closure. This left little material for the 5th season when B5 was picked up by Sci-Fi.
Thus, blame B5's bad 5th season on UPN.