You are right.
Messi was not perfect aged 18.
But also, he wasn't as hyped by stupid media and fans like Yamal is today, which will mess with his head.
Further, Messi is humble, while Yamal is a moron personality wise.
Further, Yamal's dad is probably the worst example to raise the kid.
So, Yamal's surroundings are horrible.
Further, Yamal started to play as a starter way earlier than Messi so in terms of their development, 18 years old Yamal should be compared to a 20 year old Messi.
All in all, Yamal has nice chances to turn into a biggest disappointment of the century based on his diva personality, arrogance, horrible surroundings and stupid social media apps looking for a new shiny toy all the time.
He could end as a footballing Justin Bieber or any Disney teen superstar who finished broken and with mental illness/supstance abuse later.
The kid is only 18 and he is already fighting with half of the world.
Let's see how will he overcome the hate, the expectations, the pressure and the inevitable dissapointment by the fans.