Parra, 30, who has made 71 Test appearances, a Les Bleus record in the number nine shirt, was a shock omission in June from Jacques Brunel's 31-man group as well as his reserve list for the tournament in Japan which begins on September 20.
Youngsters Antoine Dupont and Baptiste Serin as well Racing 92's Maxime Machenaud are the half-backs picked by 65-year-old Brunel.
"I'm not bitter at all. It's just like that. I believe in destiny enormously. I'm not there, no problem, that's how it is," he said.
"There are three nines there, a lot of things have to happen... (to get a call-up)," he added.
The Clermont playmaker has more international caps than the Dupont-Serin-Machenaud trio combined and he featured at both the 2015 World Cup as well as the edition four years earlier.
Parra questioned Brunel's coaching methods following the humiliating 44-8 defeat to England at this year's Six Nations and has not featured for his country since.
He was, along with centre Mathieu Bastareaud and exciting winger Teddy Thomas, the main omissions by Brunel but said his focus had returned to playing for Clermont.
"Now I have other priorities, starting by getting back with my club," he said.
Last year's Top 14 runners up start the new league campaign by hosting La Rochelle on Sunday.
France, who have appointed ex-France captain Fabien Galthie as an advisor before he replaces Brunel in November, began their World Cup preparations with a victory over Scotland on Saturday before a return match in Edinburgh this weekend.
They host Italy in their final warm-up on August 30 before playing Argentina, the US, Tonga and England in the pool stages of this year's tournament.