Legitimate interest?

I never consent to give my data away or being tracked, but how do you deal with so called legitimate interest? I tried several times to untick them but it is a long list (in fact at the bottom there is a "vendors" link with even longer, much longer list. It took me 10 minutes to get to the bottom of it once).

My questions:

-how can we trust these so called legitimate interests when they are self defined by companies whose business model relies on your data?

-how can we find out what these legitimate interests are and what data it collects?

-are such companies controlled in any way?

-is this kind of consent form compliant with EU gdpr? (normally opt out is to be as easy as opt in, and there is no "refuse all" for these so called legitimate interests).

-what are your strategies against such sites tracking you? Or am I just being paranoid?

The sheer amount vendors is daunting, the Internet really turned into crap

Edit: when clicking Preferences at the bottom the content of the legitimate interested is spelled out for each vendor, so this replies one of my questions.