We've resorted to the "scream test". When there are features that are expensive to maintain that we suspect aren't being used (based on surveys, interviews, and usability tests) then we insert a notification when the feature is used announcing it's pending removal in some subsequent version. The notification includes contact information so if we get a higher-than-expected number of complaints then we may keep the feature.
Edit: typo.
You seem to be assuming that your users are always online and not sitting somewhere isolated, the ideal place for platforms old enough that you want to stop supporting them. Telemetry only tells you if something is there, it doesn't tell you if something isn't.
Telemetry showed that users overwhelmingly approve of shitty option B!
The point of the comment is to show that telemetry is used to conclude things that aren't true, and it absolutely is, and only says the subset of things that someone wants to hear, or that even occurs to them to ask.
It's not even really a seperate issue, because even if you think you are only concerned with say how long a certain operation takes or how frequently it fails & retries, the more important issue may be why or whether that operation was even used at all in the first place.
This aspect of telemetry is simply a fact to be aware of and stands on it's own, and does not necessarily mean to say "therefor telemetry is an invalid tool that should not exist and should never be used" It just means it's incomplete at best and very susceptible to both deception and self deception.
Telemetry would fix this, but it's not our right to collect data from other people's machines. So our best bet would be to detect the condition we expect to cause problems, notify them in advance, and allow time for feedback before implementing a change.
Is it less pretty and a worse user experience than telemetry? Absolutely. But when you realize you have no right to data collection on someone else's machine, telemetry isn't a viable option, and we would betray people's trust by doing it.