One major thing that people need to remember is that literally every DLC character so far has been either a first-party from a Switch game or a third-party. Very few of Nintendo's newest games have been able to get an AT due to the timing of Ultimate's development. If new games are what they're prioritizing, then it's not particularly hard to pick someone who isn't an AT. Spring Man was actually one of, if not the youngest (and still relevant) characters to get added as an AT. As for third-parties...how many franchises aren't repped at all in Smash? Just about every third-party AT is from a franchise already on the roster, so is it really that surprising that the, like, ten or so third-party ATs didn't net us an upgrade out of the thousands of existing options?
I feel like people are focusing too hard on the idea of whether or not an upgrade is possible rather than taking a step back and asking if any the ATs line up with the DLC we've gotten so far. If we had several ARMS scenarios where an obvious choice got looked over for someone else, then yeah, I might be inclined to believe ATs matter. So far though, we haven't, and the pattern I've seen so far makes me feel like a majority of the ATs were never particularly likely even if they weren't an AT.
It does definitely feel like they're clearing the Switch backlog yes, however I think there's a cut off point somewhere that might see Astral Chain and Ring Fit out of the running. The spirit events don't outright deconfirm but the timing suggests this was al lthey could do. Pokémon is a topic all by itself, while there's lots of factors against it, I can't deny Pokémon is the biggest franchise in the world and it's a very Nintendo thing to cater to it, but thinking that's going to happen is not going to be a fun time for me.
So when it comes to Assist Trophies, a lot of them are appropriate to the series they're representing and are popular side characters for the most part (not going into whether Alucard is a side character or not. I can see otherwise, but we just got two other reps). Then there's some instances where they're the only rep to an un-represented series and sometimes their inclusion is nice and makes sense like for Yuri and Rathalos. Then there's a messy area of main characters that range from "Yeah, no one cares" to "Why would you just rule them out?!". This all gets speculative. Personally I think AT's like Dillon and Starfy, are fine where they are, but AT's like Isaac and Bomberman just got people upset. Shovel Knight too, but he's had it harder, being an indie. I still hope he gets a costume.
On top of that, there's plenty of others from existing series that people want, which leads into the point of the post. ATs imprison characters that people actually want, so usually when people go full on advocating for assist trophies, it's because there's a character they want and ATs are considered a barrier, so they will campaign for that barrier to be removed. It doesn't mean we advocate for all trophies to be promoted one day. Although, groups like Assist Alliance are certainly advocating for many, because if one is promoted then it gives hope to the others (though less so now we're down to one character).
Anyway, I'm basically saying that I want Isaac to be promoted from an Assist because I want Isaac and Golden Sun in Smash. Not because I like the idea of assists being promoted. Sure, there's a few others I like, but if Isaac got in I would probably pack up my "Well ATs don't deconfirm" attitude, and treat it as just an exception for the sake of demand (unless told otherwise).
So yeah I get that many of them simply don't matter at this point, but considering where Isaac was in terms of popularity in 2018, I think he would have been very likely if the AT just hadn't showed up. Maybe not all the way to 2021...who knows. I'd like to think so, but it's mostly third parties that dominate speculation now.
