New vs. returning doesn't actually tell you too much about retention unless the growth rate is close to zero, though? Have I got that wrong?
This seems to confirm my thoughts. My read, correctly if I'm wrong, is that after the first 10k, then you probably had to focus back on the product, thus the growth was 0 and possibly most of the 10k were gone (and the reason is usually that the product is ready for 1k, but not for 10k users).
Happy to see that now the growth is solid, thanks for sharing the numbers!
You need a cohort graph to properly illustrate retention.
Once you have their info such as email, you can always remind them, isn't it?