Greatness doesn't consistently disappear on the greatest stage. And it's not a small sample space either. It's a massive sample space.
Also success is very subjective. Relative to what exactly?
For the hype you and his admirers seem to be giving him, I would expect him to grab a European Golden Shoe or something atleast, especially when he spent his peak in France at a time when the league was shambles playing a state funded club.
I can appreciate the longevity and being around for so long but to be in the elite group you have to achieve remarkable things in your peak. There are like 15-20 players from this generation/era alone who have achieved more in their peak.
The moment Zlatan leaves Inter, they win a treble. He joins treble winning Barca and flops. Then the moment he leaves, Barca win the treble. The moment he's out of the national team, they have their best international tournament in a long time reaching the World Cup quarter finals. Then he returns for Sweden and they crash out of World Cup qualifiers. It took Milan a new striker in Giroud and making Zlatan an injury prone bench option for Milan to win the league finally yet we're pretending he's the main man. These are all facts not opinions.
Hats off to his PR team for diverting attention from his failures at the highest level and deceiving certain naive fans who get all giddy about his cringeworthy quotes. 90% of the time he's in the news is because of a quote rather than actual on-field stuff.