Telemetry is inherently bad if it's not done with the informed, opt-in consent of the end user whose data it's (mis)appropriating, oftentimes silently.

There's no issue with opt-in telemetry, where the user says "yes, it's okay to track me".

Invisible, silent, always-on telemetry is actually just spyware that's been mislabeled.

Ultimately it's not the telemetry that's at issue: it's the unethical and selfish behavior of the software/device manufacturer.

No sane or reasonable person thinks that an EULA is informed consent.