For the next one or two seasons, Lewandowski still has the ability to play at a good level and he also still has a contract until 2026 with Barcelona, but what Lewandowski needs to do is avoid injury because when this happens it will stop his steps to play at a good level. His age is indeed not easy anymore, but being able to reach 42 goals this season is a very good achievement because not many players at that age can do like Lewandowski. Barcelona could use some young players when Lewandowski is injured so what needs to be done is to recruit lower players to strengthen the defense.
I don't think you people watch Lewandowski every match. You probably just see the stats and see that he's on the score sheet. Because anybody who watched Lewandowski this season won't believe he can still be at the top level for Barcelona for another 2 years.
Without actually watching him, there's no way anybody can convince you he was not at the top level because of the number of goals he scored. Barcelona creates a lot of chances, and any half-decent striker will be able to score a lot of goals. Ferran Torres, who is the backup striker, had 19 goals as a backup; that's how many chances Barcelona create.
Lewandoski is not him anymore. Barcelona going into another season with him as their main striker is the wrong move. They need a replacement. Even if Lewandowski remains in the team, they should have a younger top level striker to lead the attack. In my opinion, this season should have been Lewandowski's last season with Barcelona, or t least his last as their main striker.