If you ask a user to show you a "core dump" they're more likely to shit on their floor and send you a photo than do what you actually mean.

Telemetry is absolutely crucial in determining what to focus on in development, to fix issues the users might not even realize exist. Especially for projects that aim at the general public. As long as it's communicated clearly, used truly only for development purposes and an opt-out is available there's nothing wrong about it.