Although I could and plan to do more to increase uptake, should I take that percentage as fairly typical? or quite bad. It seems low to me. I would have thought more like 10%.
If you only have 100 users and you're only get 5 users coming back in the last two days, you might not have hit a market fit.
If you've got 10k users, that's a different story.
But I wouldn't use a 2 day window, as I think that is too short.
I'd use monthly active users (how many users login once a month) or weekly. That should be a more valuable metric.
Again, this depends on exactly what your service does, your target market, how often you expect them to login, but 5% doesn't sound bad to me for a 2 day window.
What happens when you extend the window?