Planque, however, is quoted by French publication But! as saying: "There are still some very good young RC Lens players. This year was well-recruited with good players aged 13-14.
"What is frustrating is seeing the sometimes leave quickly, before they have time to wear the Lens jersey at the highest level. Look at Jeff Reine-Adelaide and Yassin Fortune at Arsenal. It's not easy."
Lens will play next season in Ligue 2 after being relegated from the French top flight in 20th place last term.