Bringing another striker to the team might work out well for them, but lets be honest how do you think the new striker would cope together in the pitch with Lewandowsky unless they will be starting the new striker instead of Lewandoski and then maybe during the second half they can bring him in to substitute and play for some time. Honestly he wont be Barcelona first choice of striker.
But it is indeed a problem that Barcelona's attack and defense will be a lot empty now.
This season they can still rely on Lamine Yamal and Joao as alternatives to Lewandowski but by looking at Joao's loan record which is currently over, it is certain that Joao Felix and Cancelo are absent which indirectly 2 pillars to help the attack are now reduced.
In addition, Gavi is also uncertain when to recover because seeing what is happening right now with the ACL received, it is indeed difficult for him because he needs to be re-accustomed even though he recovered so Barcelona inevitably has to look for several options that must be done because this could be a little inconvenient for them if in the end it is left with a financial condition that is not very good and with a shortage of players, it could be a bit of a headache for Xavi again and hamper performance in the next season in the end.