James is there for the new player who know nothing about Mass Effect. Since ME3 is the place the start the trilogy. I'm pretty sure Bioware even said this themselves at one point. As a character I don't actually have anything against him. I just hate that he's there at all given that I didn't feel the trilogy was the appropriate time to be introducing an entirely new squadmate - especially at the expense of 12+ others we had on the roster that weren't brought back as squadies.
Though his bits of spanish always ignored me as a lore-nerd. I mean... some of the words he uses have literal translations to english. Loco means crazy. Shouldn't the in-universe translators be, you know, translating that? I mean I understand some alien words not being translated because not everything has a good translation word to replace it but "loco" does. Infact every spanish word I remember him saying has an English translation that wasn't used.
As for Allers, well... I don't know. I hear she's part of some internet videogame show of some sort. I don't know who she is, I don't care who she is. I hated her. Why? Her voice annoys me, her character annoys me, her behavior annoys me, the "oh that flirting isn't flirting" annoys me, the overall VO quality annoys me. The concept of having a news reporter on the ship though isn't really that bad, imo. It had potential. Had they used a character that was already established in the series that has already had interactions with Shepard like, say, Emily or even the Falcon-Punch Reporter with the crazy name... I could go with that.
Except they didn't. Just like with James they decided that instead of using one of the pre-existing characters that have been established in the story already, that already have a connection to Shepard and who were already well-suited for the role.... they decided to instead to make completely new characters to introduce to us to fill those shoes. ME2 had a huge squad roster yet instead of one of them we get James. ME1-2 had established reporters that the player could interact with, who even had their own little mini quests... yet lets make an entirely new one and have her be some popular internet figure for... reasons.
Perhaps I wouldn't be so harsh on James and Allers, however, if their roles felt unique and new. Instead I just feel like the old established characters got ignored for the sake of introducing two unnecessary characters into the game to cater to newcomers of the series. At least in James' case, I don't really know what Allers is catering too.