Please define filler for me?
I mean, these streaming serialized shows usually have some overarching “season-level” plot or through-line that begins in the first episode and wraps up (or significantly advances) in the season finale. Individual episodes may advance the season-level plot to varying degrees. “Filler episodes” are episodes that barely advance the season-level plot, or don’t advance it at all. This isn’t necessarily a bad thing. Even if an episode doesn’t advance the season-level plot, it can still be used for valuable character development.
But in practice, at least with Disney+ Star Wars, the non-plot-advancing episodes can be a bit frustrating, because of Disney’s weekly release schedule and the relatively few episodes per season. The show grabs your attention with dangling plot threads, but then filler episodes force you to wait yet another week for any additional plot advancement. Of course, this is subjective and context-dependent: filler episodes can be enjoyable, especially if the show isn’t structured around some urgent season-level plot. Arguably, before serialized story-telling become fashionable, most TV shows were just all “filler episodes” - and nobody complained. I didn’t really mind the “side quest” episodes back in Mandalorian Season 1 either, because the whole show had this laid back episodic vibe. But as a show progresses and the “season-level” plot becomes more well-defined and urgent, and starts merging with larger Star Wars narratives, the non-plot advancing episodes can really be a strain.
Also, with Bad Batch in particular, I think the season-level plot-advancing episodes are just orders of magnitude more compelling than the non-plot advancing ones. Season 3 so far arguably had one “filler” episode. It was okay, I guess. It was mostly the protagonists running away from giant tentacle monsters, for the sake of a very minor plot-advancing clue at the end. (Although they did introduce those young clones, so maybe that will be significant later.) Regardless, the plot-advancing episodes are just in an entirely different league in terms of quality.