I'll just wait until my social battery is recharged enough

Eh, I'm an introvert who isn't overly socially anxious, and I'll often ignore texts for a bit if I'm really not feeling up to doing whatever it is at the moment. But I usually get to it the next day or the one after. I don't like talking to people, but I don't feel very apprehensive about it either, I just find it draining and prefer to avoid it.

Usually I'll just say, "today isn't great for me, I'll get back to you." Then actually get back when I'm more interested in social interaction. I don't feel awkward about forgetting for a couple days, certainly not to the point of ghosting someone for weeks.

Or a lack of social understanding.