The idea Red Bull were 'hoping' Albon would improve (and suddenly drive like Verstappen!) and therefore there was no spot for Vettel, sounds like typical Marko spin and lies. If Red Bull wanted Vettel they would have put him in the car for 2021, but they did not. If Vettel is a valuable 4xWDC ace, every bit the match for Verstappen or more, replacing an unimpressive uncontracted rookie with him would a no-brainer, but Red Bull did not see it that way...
It seems Ferrari valued Sainz over Vettel, and Red Bull either Albon (I mean, seriously, as if Marko can be believed on that!?) or Perez over Vettel. Thankfully Aston Martin valued Vettel highly.

The only logical explanation is that (far from Vettel being a 4xWDC ace would would match or beat Verstappen), Red Bull, instead, were concerned that Vettel would be 'disastrous' in the RB16B and it would make Red Bull look silly, it would make Vettel look silly and it would just be a disaster!
Most people view Aston Martin as the ones taking a gamble with their driver lineup, not Red Bull by picking up the reliable Perez who Aston Martin do not want for some reason.
