Jupp Heynckes has criticised Bayern Munich's failure to sign top young German talents such as Timo Werner and urged the club to spend big on the very best players if the opportunity arises.
Germany striker Werner, 21, joined Bundesliga rivals RB Leipzig in 2016 for €10 million from Stuttgart, who at the time had just suffered relegation from the top flight.
"A club like Bayern should have signed a Timo Werner from Stuttgart years ago," Heynckes said.
He said Werner "could have learned a great deal here" and added: "The best players must play -- it does not matter whether they are old or young.
"Do you think that a Franck Ribery can always expect to play? No. When he is not on form, he will not play.
"As I said, you have to look after good, young players in a timely fashion. You have to challenge, speak, lead and motivate them."
Since taking over from Ancelotti, Heynckes has given a first-team debut to reserve-team striker Kwasi Okyere Wriedt, 23, and called 18-year-old forward Manuel Wintzheimer into the squad for the Champions League game against Celtic.
"I am also of the opinion that Bayern must develop its own talented players with that special something in order to compete at the highest level," he said.
"You have to remain patient, though, because it is a process that lasts many years."
Bayern president Uli Hoeness has said signing players for a €100 million fee is "unacceptable" for the German champions, but Robert Lewandowski has warned on numerous occasions that big signings are necessary.
While strongly backing youth, Heynckes said Bayern need to spend big in the future if necessary.
"As a club, Bayern must be ready to sign an expensive top player," he said.
He acknowledged that the transfer market is difficult, though, saying: "I do think Bayern has a plan and Uli Hoeness, [CEO] Karl-Heinz Rummenigge and [sporting director] Hasan Salihamidzic know what they want. However, the implementation is not always easy. For example, you need highly talented and competent scouts to assess players -- especially young ones."