Unfortunately, Barcelona failed to maintain its best performance this season. Xavi is doing very well, but there are many obstacles that basically cannot be solved in the near future without a sufficient budget. Barcelona is only maximizing the potential of loan players, academy players and some of its old players to compete, it is clear that they are very likely to lose the competition rather than defend the title against a team that is completely adequate.
Regarding the draw against Granada, it was not something surprising. Granada knows how to stop Barcelona, in fact Granada couldn't be beaten by Barcelona last season even though Barcelona won the La Liga title. There is a rivalry between Granada and Barcelona, so it has put players and coaches under pressure. This season Barcelona has given up on La Liga, but they still have hope in the Champions League.
At least I also agree with what you said, if there are several factors that have caused Barcelona's performance to decline this season. as you said, Barcelona only relies on loan players, La Masia academy players, and several other secondary players who have to be replaced. one of them is Marco Alonso, but Barcelona doesn't have many choices because they are hampered by financial problems. Lewandowski's decline in performance, lack of optimal support from his teammates. plus, the factor of players being injured. what is more worrying for me is the poor performance of Barcelona's defensive line players and also Inaki Pena who could not be relied on when Ter Stegen was injured. as a result, Barcelona is having difficulty competing this season.
One more thing, IMO, the system that Xavi implemented is not ideal from my point of view. It's just that, Xavi is quite skilled when lobbying players to join in choosing Barcelona. even with the match against Granada, Barcelona always has difficulty when they meet this team. Based on H2H, in 5 meetings, Barcelona was unable to achieve a single victory. one match with a defeat, four more matches with a draw. well, it could be said that the probability of Barcelona in La Liga is very slim. So, Xabi hopes to be able to focus on the Champions League. even so, it is not easy for Barcelona with the team's current condition. however, let's just follow it, there's no harm in it. maybe Barca could be as lucky as Inter Milan last season.