The main theme of the show, if anything, is "love, and how it can be expressed". The show examines this not just from the perspective of Yuri and Victor's relationship, but from the relationships of everyone involved. Phichit's skating is inspired/motivated by love for his country, JJ's by himself, Yurio's by his grandfather, Georgi's by longing for his ex, Minami out of being inspired by Yuri, and so on. It's incredibly important that the show spend time on the other skaters' motivations because otherwise we wouldn't get any different slices on the main themes of the show outside of Yuri and Victor's relationship, and that would just be a poorly put together show.
There is some filler, but these are the characters that don't matter so much or don't relate to the central themes. In this episode, that would be Emil and Seung Gil. But even then these two characters are used in interesting ways, with Emil's small failures during his program helping Michele to regain his confidence, and Seung Gil being shattered by the strong performances of the skaters coming before him then being used to illustrate how far Yuri's come because he did the same thing Yuri would have in the previous year because he doesn't have anything to "love" like Yuri does. It's a great skate to compare for later in the episode where Yuri still has some trouble, but doesn't completely self-destruct like he would have in the past.
I just think anyone saying that the side skaters are "bogging down" the show aren't really appreciating how good the show is at building its central themes. The direction and editing might be taking a hit from squeezing in so many performances but I don't really care as long as the show is still interesting and entertaining, which it very much is. Despite some shortcomings with the animation lately I'd still put this in my top three shows of the year.
