Let's start with 86 Argentina; they only allowed 5 goals all tournament long. That number, no matter the era they played in, is phenomenal. This by itself demolishes the myth of Maradona "doing it by himself". Meanwhile, his partner on offense wasn't bad either: Jorge Valdano (of RM) scored 4 in the same tournament. To top it all off, he was coached by what a lot of people rightfully consider one of the greatest WC managers in history, Carlos Bilardo.
Sure, Maradona was by far the player of the tournament, scoring 5 and assisting 5. He was involved in 10 of Argentina's 14 goals in 7 matches. That is very impressive, but it didn't mean that the rest of the team were poor.
To put it in perspective, in Euro 84, Michael Platini scored 9 goals in 5 matches, including the winner that sent them to the Finals. Platini doubled in one tournament Diego's career goal total in the Copa America (4) but hardly anyone called/calls it a one-man effort. Was it because Maradona did it in the World Cup? I am inclined to say yes.
Let's talk about Napoli then. I will say upfront that I agree with everything you said about Diego putting Napoli on the map, but does that mean the rest of the squad was poor? Let's start with the defense again: Ciro Ferrera was the leader at the back of a team that conceded just 21 goals in their '87 title run. 21 in 30 games is a phenomenal record, then you add the 16 clean sheets.
Other notable teammates include Italian internationals Andrea Carnevale, Salvatore Bagni and (forgot his first name) De Napoli. Napoli was hardly Maradona + a bunch of scrubs.
Napoli was even better in 1990 as they added Careca to complete their Maradona-Giordano-Careca (MaGiCa) trio. Careca scored 73 in 164 games for Napoli.
Source -
http://www.barcaforum.com/showthread.php/1664-Diego-Maradona?p=1410378&viewfull=1#post1410378