I actually haven't seen Breaking Bad, but as a general thing the episodes often considered "filler" are the ones that provide resonance for the "important" ones.
Looking at Buffy season 2 (a show with which I'm more familiar), for example. I would argue that the defining episodes are School Hard (the introduction of Spike and Drusilla), What's My Line parts 1 and 2 (Buffy gets hunted by magical assassins, the introduction of Kendra, Spike doing a ritual returning Drusilla to health but himself getting paralyzed in the process), Surprise/Innocence (The Judge, Angel and Buffy doing the thing which leads to Angel losing his soul and joining the bad guys), Passion (the death of Jenny Calendar), and Becoming parts 1 and 2 (season finale, lots of stuff happening). That's 8 out of 22 episodes.
So could you remove the other 14 episodes? Hell no! Not only do they provide some overall plot progression, but they also get us invested in the characters. They get us invested in Buffy's relation with Angel, which makes his heel turn hurt that much more. We get to know Jenny Calendar, which makes us empathize with Giles when she gets fridged. We get to see the tension rise between the paralyzed Spike and the aggressive Angelus, leading to Spike's sort-of face turn. We see the cutesy budding romance between Willow and Oz.
Looking at Buffy season 2 (a show with which I'm more familiar), for example. I would argue that the defining episodes are School Hard (the introduction of Spike and Drusilla), What's My Line parts 1 and 2 (Buffy gets hunted by magical assassins, the introduction of Kendra, Spike doing a ritual returning Drusilla to health but himself getting paralyzed in the process), Surprise/Innocence (The Judge, Angel and Buffy doing the thing which leads to Angel losing his soul and joining the bad guys), Passion (the death of Jenny Calendar), and Becoming parts 1 and 2 (season finale, lots of stuff happening). That's 8 out of 22 episodes.
So could you remove the other 14 episodes? Hell no! Not only do they provide some overall plot progression, but they also get us invested in the characters. They get us invested in Buffy's relation with Angel, which makes his heel turn hurt that much more. We get to know Jenny Calendar, which makes us empathize with Giles when she gets fridged. We get to see the tension rise between the paralyzed Spike and the aggressive Angelus, leading to Spike's sort-of face turn. We see the cutesy budding romance between Willow and Oz.