The LaLiga champions were unable to reach an agreement with Paris Saint-Germain prior to Monday's transfer deadline.
Brazil international Neymar, who is said to be unhappy in France, could still return to Camp Nou in future, while Real Madrid reportedly remain interested.
But former Madrid and Spain boss Del Bosque believes the talented 27-year-old represents more trouble than he is worth.
"It would have been good for the Spanish league for him to return but if I was involved with a club, I wouldn't have signed him," Del Bosque told RTVE programme Estudio Estadio.
"He is a great player, but there are other things I don't like. He did not behave well at Barcelona. He behaved badly, or very badly.
"If you did a survey in Barcelona, there would surely be more than 50 per cent who would be reluctant to have him back."
Another of the close season's transfer sagas took place over at Del Bosque's former employers Madrid as Zinedine Zidane unsuccessfully attempted to remove Gareth Bale from his squad.
The Wales international appeared destined for the Chinese Super League until Madrid's board blocked his departure.
Bale has since returned to favour, starting each of the club's three LaLiga matches this term, and Del Bosque thinks the four-time Champions League winner will prove useful to Zidane.
"No one thought his behaviour was bad, just that he did not adapt to Madrid. Very few people doubted his qualities," the retired World Cup winner said.
"I think he will perform for them because he is a very good player."