Flik is very different from Guardiola, and of course he will build a team in his own way. The coaching headquarters is also very important for working with the team, alone Flik will not oto cover everyone, and even more so when you mentioned the language barrier, this is also a very important point that you need to take into account. Flik is a good coach, he worked with the best of the best, so I think that he should be no worse than Xavi. Xavi achieved good results despite his little experience and a short career, so Flik should be definitely no worse, and perhaps even better than him.
Only hope that we might be able to do today, we don't know how Flik will bring the best thing to Barcelona which is rumored to have suffered a setback for this season due to the departure of Xavi, it's natural for people to say that maybe they haven't seen what Flik can give to Barcelona, the season hasn't started yet, we can't say that far, maybe just speculate about the possibilities that Barcelona might get by employing Flik.
But it seems to take time, I'm not so confident in Flik despite having a good experience so far in his career, but yes that doubt cannot disappear until we see how it goes this season, at least Flik maintains the position that Barcelona occupied before Xavi left.