I think people are so eager to take offence they don’t even try and engage with the subject matter or question being posed. You can be both a nation’s greatest player and still not have filled all your potential.
If Kanu had been touted as a player who could challenge for an all-time top 10 place, but falls short of that, by say, 15 places (subjectively tiered lower), he is still, without question an amazing player who has had a career the envy of others, but relative to those he was potentially peered to, he still fell short.
Geroge Best is Northern Ireland’s best player of all-time by an absolute mile, yet he could’ve been more, by some distance, if he wasn’t dragged into the mire of alcoholism and off-field antics that consumed him.
You can be amazing at something, yet destined for more than your eventual lot, the argument then becomes how much of the aforementioned potential you fulfilled, hence the thread, which is valid and should be discussed rather than scoffed at.