Lewandowski is already 36 years old, but he can still be relied on in the front line, this season he was recorded as the top scorer in La Liga, seeing other clubs that are still interested in recruiting him, it would be a big loss for Barcelona if they let him go as a free agent.
Barcelona also cannot rely on him for too long, his increasing age will greatly affect his performance, so far, Raphinha and Yamal are still very consistent in maintaining their performance, Barcelona needs to find a successor to Lewandowski who can be relied on to form a new trio on the front line.
At least for this season Lewandowski is still a mainstay who has made such a big contribution to Barcelona that letting him go is not a good decision even though he is no longer young. Barcelona must find a replacement first if they want to let Lewandowski go so that his departure does not cause a much bigger problem. Being the top scorer in La Liga is something extraordinary at his age now and the level of productivity is much better from season to season, this is what makes Lewandowski more mature at his age which is no longer young.
36 years old and still the highest goal scorer in La Liga, his age could be telling but his presence in that squad is of great importance, he has contributed to the team, it's not about agility but at times experience helps the team. Barcelona should find a replacement but not let him go at the end of the season, they should extend his stay by another season then once in a while play him and then another play the new striker, he wouldn't be getting much time on the pitch though but having an experienced striker can help them at a point in need.