[GuidoK]

So on what basis should passing be possible if not because of DRS, not because of pace difference and not because of mistake by the other driver?

It even used to be way more difficult to pass in F1

The only thing I can imagine (and which is already partly in place) is a spending cap, to give 'lesser teams' the same chance to develop a competative car (although from a historical standpoint F1 should be about the highest level of technology imho), and that engines should either be sold by an independant broker. That last measurement takes care of that teams can't influence other teams. So a manufacturer either doesn't sell their engines, or they sell their engines but for a fixed price (I think that that may already become a rule) and have no say to whom they sell their engines.

Although the budget cap might result in the future in a very undesired direction, like it has happened with virtually all industries that need to compete on price....

But regarding sunday's race, nothing significant would have changed the outcome of the race if passing was no big deal.
Max passed HAM and BOT on talent. He managed to get a little slipstream from BOT, placed his car next to BOT on the racing line and managed to break really late. All on talent, no DRS needed.
The only thing we would have missed this race was the excellent fight between BOT and RIC for 10th place or so, were BOT would have passed RIC right away, but the top 5 was never really within striking distance so that would have stayed the same imho.
So all in all we would have had a more boring race in Mexico if passing was easy....