This is why I often say it's too hard to tell who truly are the best managers in world football. Pep and Jose have the most glamorous of CVs but their success is fabricated on the basis of only ever managing the best clubs during a certain period. Although I can never prove it so I'll admit it's not a valid point but I'd be relatively confident that if say someone like Eddie Howe was given the opportunity to manage Barca/ Bayern/ Real etc, he'd likely win just as much as the others.
I think, like you say, it's hard to tell sometimes.
Just some examples:
Zidane won 1 league title and 3 consecutive Champions Leagues in 3 years. That's honestly a phenomenal achievement. And whilst he did have awesome players inherited, even greats like Sir Alex Ferguson or, in his prime, Jose Mourinho were not capable of something as astonishing as that.
Zidane was able to leave Madrid with his reputation in tact. Not many managers can say this. Ancelotti and Benitez, both managers with higher managerial pedigree and clout than Zidane, ended up getting sacked.
Yet when he was suggested as potentially taking over at Man United or Spurs, a sizeable number of fans from both clubs had their reservations about him as being manager.
Barcelona sacked Gerardo Martino after failing to win a single trophy in 2013-14. You'd have thought he'd be able to win at least one trophy with that world-class squad, but he couldn't. So sometimes it's not as straightforward as having 'just anyone' to achieve that scale of success.
Claudio Ranieri flopped at Chelsea, Valencia (twice), Napoli, Juventus, Roma, Inter Milan and Atletico Madrid. I think he ended up getting fired from each of those clubs. Yet he ends up winning the league with Leicester City of all clubs

And whilst he will take the plaudits for that season, Leicester's good form from the end of the 2014-15 season continued into the 2015-16 season. So does Nigel Pearson deserve credit for creating the base of that title-winning squad?
The point I'm making is that sometimes there are just too many variables at play when determining who is an 'elite' manager and who isn't. Some managers walk into clubs with very little disruption and the perfect conditions anyone could ever wish for, others don't get that luxury.