They spent the whole season without their centre-forward and reiterated that they were a great team, first winning the La Liga championship and then the Champions League. There was only one cup missing, I think, with the Mbappe transfer, they became candidates again for all the trophies that can be won next year.
Xavi has left the Barcelona side and it should only be a matter of time before the team announces new transfers. Yes, first of all, Barcelona needs new players to organize its fragile defensive line.
You say they don't have a striker, but you forget the Bellingham factor, who scored in every game at the start of the league and brought them wins. In those games Bellingham always played like a striker and went inside the penalty area. Later, when Vini Jr. returned, he made a significant goal contribution. Joselu, who nobody liked, who was seen as a backup striker, worked wonders. Rodrygo and Diaz scored goals. Real had no goal problems. They had a very strong offense even without Benzema. They will be the favorites next season too, because it's still unclear when Barca will overcome the economic crisis they are going through.
Bellingham is not a striker, it was only on how smart and tactically coordinated they were able to secure all their wins. It took them a lot composure to be able to win everything they won whereas if they had a standard striker it would have to be a lot easier for them. All they have to do is to work out out the opportunity, create chances and passes then give to their striker to do the finishing, I hope they stick to finding a permanent striker. With the involvement of Mbappe they still retain their stand as the best and a lot they will achieve coming season.