Buying players may not be priority for Barcelona this season especially as they are not financially boyant enough to shoulder such bill they may rather just have to improve their performance with the team they have got already that way it will save them cost and they will optimize their team depth.
Xavi may have the intention to sign new players, but the Barcelona management probably has no enough money for new players. If Xavi wants new players, the only option is to get from Barcelona Atlètic. Xavi actually has done the option, he already take some players such as Ander Astralaga, Fermín López, and Lamine Yamal.
They have still got good players after all except for the case of lewandoski they have almost little to no case of injury this season so most of their players are still in good form and strength to be able to make sure they get the best out of this season. Barcelona just needs to further work on their tactics and they players positioning aswell as rotation when possible amongst players, that way they get to maximize the squad except they may opt in for a loan where necessary.
Yes, there are many good players in Barcelona squad. But many of them can't play in their best form nowadays. Not sure what's happening with them, it may be caused by the tactics or low motivation in playing. Or it can be the impacts because some players got injury for a long time. Lewandowski is one of the player who experienced this problem, he can't play at his best level anymore after he got severe injury.