Emails are hit and miss, I would say more miss than hit. Something in-app is better.
But is it a major improvement for users?
We have a tendency to think that if something was hard to implement it is major or important. My point is don’t cry wolf. Better to restrict annoying users to things that are significant.
If the adoption rate is low you also have to ask yourself if it is solving a pressing business need and whether the UI is a bad (I always assume it is worse than we think). This could also highlight that it is a minor improvement, niche feature.