> I believe most of the site-owners need these information to operate/develop their sites
Can you give an example of a piece of user-relevant functionality that cannot be implemented without Google Analytics?
> it seems like a lot of work to implement those in-site tracking features yourself
Aren't there libraries/frameworks/products for exactly this? E.g., when I google "website tracking framework" amplitude.com is top ad result and http://google.github.io/tracing-framework/ is the first non-ad result.
> So, if anyone could simply explain why this is SO bad or send me to correct discussion
Informed consent. Cookie blockers and Firefox containers provide the technical tools that enable me to make an informed decision about whether to use your site. Without those technical mechanisms, it's very difficult for me to constantly monitor whether you are tracking me.
You/Google are free to deny me access to your products/content if I choose not to be tracked. But I should be allowed to make an informed decision about whether to use your site.