it was advisory, degs.
what went wrong are three things:
- Team Brexit had (and still have) no coherent plan if the referendum went their way.
- The (unelected) EU Presidents were/are being very difficult.
- The media have been on Project Fear overdrive, sowing even more division amongst the folk then there was before.
Smartest guy in the world, yet doesn't know this rather basic fact. The President of the European Commission (Juncker) is nominated by the European Council (who, lest we forget, are the elected heads of the 28 member states), before then being voted on by the European parliament, who have the final approval/veto on the appointment.
The President of the European Council (Tusk) is selected by the elected heads of the 28 member states. If you want to get pedantic and say we don't vote for them, then we don't vote for the prime minister either, as they're chosen in the same way by their party.
The President of the European Parliament (Tajani) is elected from MEPs.
So all three presidents in the EU are chosen by elected representatives.
https://europa.eu/european-union/about-eu/presidents_en has all you need to know.