You should have a ton of telemetry on business metrics. You would absolutely notice an issue before your users if you have those. For example at Netflix we monitored stream starts per second -- how often you hit play and it worked. That metric was the most important, and the one that triggered most investigations.

If your CPU and memory aren't affecting the business metrics, then it's not super relevant.

Very little harm... If the telemetry is from your users I'd like you to value them more than that.

Also consider the potential risks of handling personal data and leaks.

This only holds if you assume telemetry means personal data, but that is a very big if. Meta, Google and other giants generally deal in telemetry that includes personal data, however for most run of the mill software that's not the case. Outside of advertising, I would argue that for most applications you're already pretty close to being clear of personal data as long as you exclude the user's email and other identifiers from the logs. Sure, there are examples where this is not the case, but it isn't even remotely as big of a problem as you claim it to be.

A lot of telemetry can become personal data. Filenames etc. are the easy parts.

Telemetry needs to be motivated for it to not be considered spyware. You need to really consider what you are logging and why, and then, is it worth the downsides.

It is not something to take lightly, hardly "no harm".

Very few things are worth keeping after two weeks, I like short retention policies

As someone who's been on a maintenance team for years, keeping monitoring (cpu, memory, disk, etc) for at least two weeks is critical, and I'd prefer 6 months to easily identify larger trends and prevent issues before they happen.