I used to be quite hardline on this matter myself, but I found the julialang [1] discussion on this topic quite a persuasive argument in favour of default telemetry.
I think it's a difficult ethical question, because there are balancing concerns and interests, and most behaviour doesn't easily fall into the obviously wrong or obviously right categories.
There is a difference between, say, Debian popcon (which is opt in during install) and the 50 MSFT tracking options that are enabled despite having ticked the "no" box during install.
One of which is a keylogger! Windows 10 is pure evil.
"As part of inking and typing on your device, Windows collects unique words—like names you write—in a personal dictionary stored locally on your device, which helps you type and ink more accurately.
If you sync your Windows device settings to other Windows devices, your local user dictionary (up to 100 KB per language and 300 KB total of hard drive space) will be stored on your personal OneDrive for the purpose of enabling sharing of your dictionary with your other Windows devices. "
And it may have been worse when Windows 10 was first released:
It doesn't. It creates statistics on how you type and what words you use in order to predict your input in order to help you in the future by predicting words you'll use before you type them.
It also doesn't do this for password/passphrase fields.
You can also turn it off, and you're prompted to do so upon OS installation, and the option is always there in the settings application, and you can even tell Microsoft to delete any telemetry it has for you, if you want, and they'll delete it.
Those are the facts. But, it's common to ignore those and just shout "keylogger" in online forums. It is also, somehow, a sign of weakness if you look for updated or changed information which may change your opinions, because no one ever seems to do this. Like, ever.
I think it's a difficult ethical question, because there are balancing concerns and interests, and most behaviour doesn't easily fall into the obviously wrong or obviously right categories.
[1] https://discourse.julialang.org/t/pkg-jl-telemetry-should-be...