Assuming Xavi is still the coach, Barcelona will still be in second position at the end of each season until the club is strong enough to win Laliga, but currently that a new coach has taken over I don't know ifit will be a problem for Barcelona to finish second in the table next season. Flick is a good coach and I believe he will be supported by the management but it might be difficult for them to win Laliga till they have the players that can outsmart Real Madrid.
Olmo is a good player and very young, if he comes to Barcelona it will be an advantage to them because the team will improve in performance. He can play along with Yamal if he is not sold out and their attack will be strong. However, it will take the coach time to strengthen the team to win trophy but with time he can turn Barcelona into a team that use to be a nightmare to Real Madrid.
We can't compare Xavi Hernandez to Hansi Flick because they're both different and possessing likely similarities. Barcelona will bounce back to formidable form, all they need is enough time to heal from the severe critical injuries that have hits the club and also affected them so badly. Barcelona president, Joan Laporta will always push for excellent results and we know his next plan for the club.