The writing can be a little hack, but clearly the animators put a lot of work in. The whole creepy art-deco design of Gotham is really good. Plus there’s lot of cool effects, like Two-Face’s other face being shown in lighting.
I’ve been giving it a re-watch and have been surprised at how good it is.
The April Fools Day episode gets a rewatch from me on occasion, mostly due to the special music theme. It’s also just a fun episode of Joker doing his thing. Oh, and the side bit with Alfred is so dry yet silly. I think the intro for the series is also completely iconic for animation and Batman aesthetics.