I did the same for many years, blocking third party cookies, having a different browser profile, but none matters. Recently I downloaded all my fb data and I found that fb gives a tool to advertisers where they can upload my contact information to join all the dots. The heading says "Advertisers who uploaded a contact list with your info" https://imgur.com/a/FRsUP
That's kinda the opposite. The brands somehow had your info (from accounts you may have created with them, for instance), which they explicitly imported into Facebook specifically to show ads to you etc.
All this information is collected to connect all the dots.
When I was going through the advertiser list, I was kinda shocked coz I never give my any detail to them, and still they have somehow uploaded it to fb. FB should ask the advertisers about source of data.