Hmmm, yes and no.
That Del Piero is primary a local Juve legend is a fact, but that's the case with most of the legendary players. But he's also very famous worldwide and for some reasons (which have to do with his quality as a player, with lasting long, with his character etc) he is respected world wide.
What you mean is that he's not a world football legend like many other players are, who are rated the same both by the world and by their local clubs. Players like Maradona, Zidane, Messi, Ronaldinho etc. With DP that's not the case because he's rated much higher locally than internationally (but this doesn't mean that he's not rated high internationally)
That's true and it's because he, almost never, was among the best 3 players in the world (for example, he never made the ballon d'or top 3 in his 17 year old career.) To be a world legend you also need to be consistently the best or among the 3 best in the world, the way Maradona, Zidane, Messi were/are.