The PSG move changed, or perhaps, revealed his personality, and he has been very disappointing in terms of handling being 'the man' on the European stage since that apparent elevation.
He went to PSG and initially had all the spotlight and attention on him (before the arrival of Mbappe) and he hasn't carried himself like a potential all-time great is supposed to in terms of leading the team, either by example or by being their beacon of hope.
He wasn't fit, or at least 100%, at the World Cup, and he compensated for that by acting like a theatrical diva, which was a let down. If he was wary of being tackled and felt his pace and form weren't there, he should've utilised a minimalist approach instead of going the other way and becoming a ball-hogging drama queen.
The biggest problem with Neymar is that what he is is intrinsic in a way that's unique even amongst the elite of the game - he was a superstar, saviour of the planet during his formative development. He wasn't protected or nurtured in the way Messi, Rooney or any other child prodigy I can think of was; he was outright paraded, told, displayed as 'the one' who will be the next true great out of Brazil. Not even Ronaldo (nor Ronaldinho) was projected as that at such an early age, and it simply has to do something de-constructive to the mind if you've not got good people around you, which Neymar didn't, so his moments of good behaviour and playing fiddle in line with others, or even forcibly accepting he's a tier below someone else, all of which happened at Barcelona, is actually the outlier in his career.
I don't see him changing for the better in terms of ego and antics unless there's either a massive public backlash against him - not just a brief moment of memes on the internet, but actually him being a solid talking point on football shows etc around the world - or a moment of epiphany where he realises time isn't on his side and he is letting himself down as talents around him challenge for the #1 spot once the '2' truly wind down and relinquish it, over him. I think the moment someone wins the WPOTY not named Messi or Ronaldo and it's not him, is the time he will have to take a step back and have a think because he has thought and been told, since god knows how long, that that crown will be his and bought into it wholeheartedly.
PSG might have brought him spotlight and attention that he craved, but developmentally, it's been a costly exercise at a time when he should be taking his game, and his approach to it, to the next level. If he does finally get his move to Madrid, it will be interesting to see if it's the true making of him or whether it'll be a continuation of the petulance that he's infamous for - really couldn't call it either way.
btw, that clip in the OP is no display of him being a brat. It shows he's a competitor and won't accept being outdone even in a lower level game - something that is rife amongst big players.