Trixie's actions purely from the episode she was in make her a more complex and better written character than "Captain British of the Britishkateers," and she (as was Gilda) was central to the episode storyline and drove what was going on.
Trixie is a showboating, haughty starlet thrust into a situation way above her ability to solve for reasons that were partially her fault; but she tried to do so anyway and then refused to eat the humble pie when it was served to her (so she didn't even try to learn her lesson like, say, Rainbow Dash would). Gilda was a short-tempered bully who nonetheless clearly did care about Rainbow Dash and wanted to spend time with her, but responded towards Pinkie Pie getting in the way of that by being a complete bitch to everyone who wasn't Rainbow Dash and also refused to learn her lesson (throwing away her friendship with RD in the process).
That doesn't mean that they are suddenly the good guys, and that doesn't mean that their actions are justified. And whatever backstory fans want to chalk that complexity up to is purely on them. But that does make them relateable characters, and that is the mark of complexity.
At the other hand of the spectrum we have Pip, who was shoved into his episode at the expense of the main characters of the show (to the extent that they had a scene planned out for Rarity interacting with Luna and then scrapped it) purely to act as a morality pet B-Plot that was both unnecessary and could have been filled better by existing characters regardless; and in a show written with a level of medium awareness about colorful cartoon ponies who sing songs and live in harmony with each other, to play a character archetype such as his completely arrow straight with no other features to his personality to it is almost farcical. Even the Flim Flam brothers, who were lifted directly from post-war musicals right down to their clothing, at least had a fun song and drove the storyline for the episode.
However, I prefer the cute light-heartedness of an admittedly pointless though sweet and endearing side-character over the bitchy, unchanging, unlearning stubbornness of a couple of hot-headed, equally stereotypical villains; at the very least, Pip actually learned to conquer his fear of Luna before any of the other younger ponies (obviously not including Twilight) did, and is thus a changing character who undergoes positive development - whereas Gilda and Trixie are just complete bitches through-and-through, and stay negative from their opening lines to their last.
Having said that, I understand that they're something of a "perfect bad example" as an antithesis to the mane six, and are thus instrumental in teaching Twilight the particular "lesson-of-the-week", so in that respect, they're entirely necessary - I just find them completely dislikeable as a result of what they do, and the only positive changes that we see through them stem from fanon interpretation and speculation.
I can see why they were great for the subjects of their episodes, but I don't at all like their personalities. Pip, on the other hand, isn't so much a great character as far as his necessity in the show goes, though is likeable for be a nice, innocent and actually quite courageous pony.
(I'd pic a Trixie shipfic over a crappy Pipfic any day of the week, though)
👍 !
