- The acting. How did they get away with this? It's at least as bad as the old Star Trek. The guy who played Sheridan is probably the worst offender. Post-season-1 Delenn is pretty bad, too. It's like John Connor taught her how to smile. (If it were deliberate, this could have been used to the show's advantage. Delenn rarely looked sincere, even when she was supposed to.) On the other hand, some of the cast members were really good. It's weird.
- The scripts. The over-arching plot is great, but the actual writing in many of the episodes is pretty appalling. It reads like a first draft: it lacks subtlety; large sections of the plot are spelled out in dialogue; there are too many convenient coincidences.
- The moralizing. JMS is prone to Heinlein-style speechifying. I'm willing to forgive a certain amount of that if the ideas being presented are fresh and interesting, but a lot of Babylon 5's speeches consist of cereal-box wisdom and cliches. Even when nobody's actually giving a speech, many episodes have rather blunt messages.
- Too many homages. They're fine once in a while, but they need to be subtle and infrequent. They shouldn't draw attention away from the rest of the show.
- Many of the characters stagnated. In one of the early commentaries, JMS had claimed that nobody on Babylon 5 was who they appeared to be. Alas, apart from G'Kar (and Londo, for a while), everybody turned out to be exactly who they appeared, and stayed that way.
Wow, that looks harsh. On balance, I like the show; but there are far too many things that bug me. I think I'll take a break before going on to season 5.