If you mean it didn't have characters you like, most of them weren't invented yet or too recent to have been considered at the time.
The show had some duds, but re characters that were represented were generally consistently better than they are in the comics. Bruce in particular was a thousand times better, as were most of the villains.
The Joker is an extremely overrated and one dimensional character. He is uninteresting and would be killed in a second against any other hero other than Batman.
Honestly There's A Batman in my Basement is probably the worst episode and its not really all that bad. It's just a very kid centric episode, it is still a kid show after all. There are some weak episodes but I don't think there are any "bad" episodes. I watch the show regularly, the animation and voices are always fantastic and it holds up tremendously.
"It's too bad she won't live! But then again, who does? - Gaff Blade Runner
"In a short time, this will be a long time ago." - Werner Slow West
"One of the biggest problems in the industry is apathy right now." - Dan Didio Co-Publisher of I Wonder Why That Is Comics
Fact!
I really REALLY hate the way GL's have turned into Cannon Fodder. When a Green Lantern died it should be a monumental affair. Crisis on Infinite Earths had an epic battle in that killed like 6-10 Lanterns I think... Everything Post-sinestro war... Those rings are flying all over the place searching for new recruits. Really dulls down the franchise to me.
Naturally there were bad episodes. But that's not what people tend to focus on... it's always how this was the 'perfect' Batman franchise.
Honestly, I loved it at the time too... but it feels a bit dusty to me now. The whole 'crime/mystery/resolution within 22 minutes feels rushed and weak now days. There was never enough Robin in the early episodes. Out of the whole Volume One DVD set, I think there were only three that had Robin... and they were my favorite episodes of the set. (Along with Heart of Ice and Feet of Clay of course). The two parts and the 'movies' they did were able to stretch things out better for pacing... and were really REALLY good.
I didn't care for it as much when they switched art styles and brought in Tim/Jason... I also actively disliked Timm's DCAU when Justice League took off... but the original BTAS was very good. Not perfect, but very very good.
I think people consider it the pinnacle more because, to date, it's probably the best balance of fun and serious, all the important characters are represented in some way, and the atmosphere and designs are near perfect. Its Batman distilled to his essence aimed at as wide an audience as possible.
The lack of Robin in most episodes didn't bother me. He's a supporting player, not the star. The set up of Dick being in college is my favorite because it provides a solid reason for him not being in every story. Could have used more Batgirl, but even she shouldn't appear as often as Robin.
I too dislike the change in art styles. The oroginsl seasons original season's are still the best. I would still take the later episodes, in content and design, over the majority of Batman products since then, though.
Gonna say it! With all this Green Arrow talk I might as well. He's the only big time character at DC that I kind of find... boring. Keep in my I haven't read the legendary Mike Grell book.
Actually, out of the 5 BIG Silver(Or Golden in Oli's Case) Age characters who got replaced for real (By which I mean for more than just a temporary stunt) by legacies (Oli, Barry, Hal, Kara, Babsgirl), Oli is the only one I don't find boring. Never liked Hal or Kara (Really, really HATE Kara) and while I used to be neutral on Babsgirl and like Barry, what's been done with them in recent years has driven me to hate. Oli's an asshole through and through, but he's got a good heart deep down, an even deeper pot of chili, and he's almost as left-wing as me...Connor Hawke is still a vastly superior character though.