So any instance admin can analyze all users upvotes/downvotes and possibly derive political standpoints, likes/dislikes, opinions and location data from it

So you can get the users voting on posts on other instances?

Could it be anonymized, so you can get exact up/downvote data from your instance, but when it comes to other instances you only get the absolute up/downvotes?

I agree, someone has to store and maintain your data, but giving all instances access to it is a risk that could be avoided

I get your point, but third-party app stores are optional. You can still only download apps from THE App Store.

And I get what you mean, when it comes to the longevity of devices. I feel like this will change in the future, but time will tell.

When taking into account, how much of Windows has become Linux, the percentage should be much higher.

Edward Snowden remarked:

Arguing that you don’t care about the right to privacy because you have nothing to hide is no different than saying you don’t care about free speech because you have nothing to say.

There is a wikipedia article regarding this argument