With Ferrari having elected to rehire the Finn for next season as Felipe Massa's replacement, Fiorio thinks that the outfit may have been better off taking a youngster with more potential for the future.
"I'm not a fan of the new hiring," Fiorio said in an interview with Gazzetta dello Sport.
"I admire his talent, but I don't agree with his lifestyle and his technical approach. I wouldn't have gone for him.
"In my opinion it's a conservative choice. I would have gone for an emerging driver rather than one at the tail end of his career.
"He doesn't live like an athlete and to be champion in F1 talent is not enough.
"You need physical, technical and psychological effort and, from what I know and have seen, he's the type of guy who takes his bag and leaves shortly after the sessions.
"I don't know how much technical contribution he can bring."
Fiorio, who worked at Ferrari from 1989 to 1991, thinks that Raikkonen's arrival at the team will actually be of benefit to Fernando Alonso - because he is convinced the Spaniard will come out on top and enhance his reputation.
When asked if Alonso will suffer from Raikkonen's presence, Fiorio said: "Why should he? In my opinion Alonso is happy: his worth will grow by beating him [Raikkonen].
"I don't see any problem ahead. In any case, the new pairing will be the strongest in 2014: the Mercedes pairing is close, but [Nico] Rosberg is very inconsistent, he does exceptional things and then disappears.
"Kimi instead is a hammer in the races, a fighter, even though he's not an ace in qualifying."
Although there have been suggestions that having Raikkonen and Alonso in the same team could cause political tension, Fiorio reckons the situation is easier to manage than having only one top-line driver.
"I think that it's better to have two champions and having to deal with a rivalry problem three or even ten times a year, in the knowledge that both are able to win races and championships, than having a useless number two race driver," he said.
When asked if he viewed Massa as useless, Fiorio said: "I'm just saying that in the last four years Massa has waned a lot.
"His only strength was the single lap, but he has no race quality, has no rhythm, and he often fades in the races."
Translation by Michele Lostia