I don't think a good name for this exists, and I don't think we need one. It's usually better to talk about the specific cause areas than to try and lump all of them together as not-longtermism.
As you mention, there are lots of different reasons one might choose not to identify as a longtermist, including both moral and practical considerations.
But more importantly, I just don't think that longtermist vs not-longtermist is sufficiently important to justify grouping all the other causes into one group.
Trying to find a word for all the clusters other than longtermism is like trying to find a word that describes all cats that aren't black, but isn't "not-black cats".
One way of thinking about these EA schools of thought is as clusters of causes in a multi-dimensional space. One of the dimensions along which these causes vary is longtermism vs. not-longtermism. But there are many other dimensions, including animal-focused vs. people-focused, high-certainty vs low-certainty, etc. Not-longtermist causes all vary along these dimensions, too. Finding a simple label for a category that includes animal welfare, poverty alleviation, metascience, YIMBYism, mental health, and community building is going to be weird and hard.
It's because there are so many other dimensions that we can end up with people working on AI safety and people working on chicken welfare in the same movement. I think that's cool. I really like that EA space has enough dimensions that a really diverse set of causes can all count as EA. Focusing so much on the longtermism vs. not-longtermism dimension under-emphasizes this.
I think it's especially confusing when longtermists working on AI risk think there is a non-negligble chance total doom may befall us in 15 years or less, whereas so-called neartermists working on deworming or charter cities are seeking payoffs that only get realized on a 20-50 year time horizon.
True; empirically there is a lot of crossover in 'which risks and causes we should care about funding'. In the other direction, pandemic prevention seems to serve both masters.
But, for clarification, I think
the reason the "longtermists working on AI risk" care about the total doom in 15 years is because it could cause extinction preclude the possibility of a trillion-happy-sentient-beings in the long term. Not because it will be bad for people alive today.
"deworming or charter cities are seeking payoffs that only get realized on a 20-50 year time horizon" ... that is only long-term in common parlance right? It's not long-term for EAs. LT-ists would general not prioritize this.
As a personal example, I work on AI risk and care a lot about harm to people alive today! I can't speak for the rest of the field, but I think the argument for working on AI risk goes through if you just care about people alive today and hold beliefs which are common in the field
- see this post I wrote on the topic, and a post by Scott Alexander on the same theme.
Everyone dying in 15 years certainly sounds like it would be bad for people alive today!
But yeah it's more about the stakes (and duration of stakes) rather than the "amount of time to effect"