If you want to go that route
City beat Bayern and Madrid won the CL unbeaten
Mourinho Porto lost home and away to Madrid in the groups went through Man utd Lyon Deportivo and Monaco. Tell me a weaker route for a winner in recent years.
Mourinho coached Ronaldo and Kaka 2 players who won balon dor before meeting Mourinho plus Sheva and won 0 CL with them
Pep coached Messi Xavi Iniesta Busquets Debruyne into GOAT conversations
Did any of Ozil Fabregas Deco get into those conversations
Players like David Silva reached New heights under Pep as did many City players
We didn't lose to Real away in 2004, we drew.
Also that Deportivo team was very strong, they lost 4-1 away to AC Milan's super team then trashed them 4-0 at home.
Monaco eliminated Real and Ranieri's Chelsea that in turn had eliminated invincibles' Arsenal.
Lyon was very strong as well in this era.
This wasn't 2023, there were several strong teams and the scales weren't as unbalanced back then.
Also this years' Bayern and Real were still contenders to the CL as some of the best teams but they're not truly great this year (Bayern almost lost the bundesliga and Real had a close race for 2nd with Atlético).
Mourinho coached Ronaldo and Kaká (past his prime) with Real, in the 6 years before he came Real had been eliminated in the R16 every single year.
He brought them to 3 semi finals, losing one to a super Barça, another on penalties to Bayern (way less embarassing than losing to a subpar Chelsea with super Barça) and Dortmund which was yes a clear bad result (team was already imploding before though).
Compare that to Pep's Bayern, in the previous 4 years they had reached 3 CL finals (winning one, the year before) and he didn't get to reach one in his time there.
All those 3 players were amazing under Mourinho, Fabregas had been good for a long while in a titleless Arsenal, Deco was with Rijkard for a while and Ozil had 1 good year with Arsenal... but this is... his fault? How?
Silva was already amazing before Pep. Remember that 6-1 for instance? City already had some very good players.
Pep's City had embarassing losses every year in the CL except this year, for such a long time prepared and expensive team is that good, 1 CL out of all that?
Pep has the merit of putting that super Barça team togethern (just note however that Barça had won the CL 2 years before...) but do you really want to compare the treble Bayern and Oilchester City to what Mourinho had been doing?
Mourinho put up together with pennies a UEFA cup + CL winning team with Porto, then went to Oilsea yes but they had won nothing before and had just starting the money flow, he didn't win the CL here and that is a fail.
Then he went to Inter and in Europe (in italy it was a formality due to calciopoli) in the first year was meh, sold his best player and put up a team to win a CL (again with not a clear favourite), eliminating Pep super barça.
What does he do next? One of the hardest jobs - go to a european humiliated Real (for several seasons) and to face directly against super barça. Real suddenly gets 3 CL semis, beats barça in the league, turns the tables later in his stint and barça struggles to beat real 1 on 1.
Then he goes to a meh chelsea, wins them the league.
Then a thrashed united, with terrible years and a terrible squad (compare this to Pep arriving at a very good City team that had been champion 2 times in the 4 years before iirc).
Mourinho wins 2 cups (and CL access) and Pep ends up 3rd (iirc). Pep is showered even more money to join his already quality squad. Next year Pep gets 1st place, Mou gets 2nd with a much much worse squad.
Mou eventually leaves Utd mid year in a civil war and goes to might be top 4... Spurs.
City keeps getting more and more money, wins some leagues, is beaten in the CL by everyone.
Now after years and years of managing CL winning teams he finally does it once. Yay...?
Don't get me wrong, Guardiola is a good manager and his style works very well if he has the players. But notice the big IF.
He needed 10 years in some of the strongest CL winning squad to win the CL (Bayern + City). Is this GOAT level?
He is an excellent manager that has been riding the circunstances, he never had to struggle with a team, he was handed great teams out of the bat (with the exception of the first year of the barça team he created).