It’s not thaaat soft. It’s not quite clear what it means, exactly. The courts still have to work that out. But you will not get away with just any argument.
It’s never legal to collect more data than necessary and/or for an unspecified purpose.
Tracking for personalized ads could be based either on consent or on legitimate interest. If it’s consent, then they need to tell you up front what specifically they use the data for and some other things. If it’s legitimate interest, they can just start doing it, but still have to tell you afterward and also inform you that you have the right to opt out.
I guess, practically, whether a company claims one or the other is whether it feels lucky about a court case. With consent, you are on the safe side but it’s a little harder to get. Legitimate interest may get you more ad money in the short run but eventually, maybe or maybe not, a fine.