It wasn't entirely Lewandowski's fault, but if you look at the attacking lines of the last 15 years, then they are now not even close in quality to what they were used to at Barcelona. I understand the frustration when they are still longing for two strikers like Suarez and Messi, The attacking line Barcelona now has is much weaker. But it is not only the attacking line, it is the midfield and the defense that are both not as strong anymore.
Real Madrid made a lot of right decisions. Barcelona has some great talents, but they don't have players that are so decisive like Vinicius Junior or Bellingham. I also think that Real Madrid's defensive players are stronger in aggregate than Barcelona's defensive players.
Lewandowski will never be able to play alone without the support of his friends so blaming himself personally is not appropriate. Barcelona is experiencing setbacks this season and although the condition is not too bad, it is quite affecting the players' performance because this club has big names that are constantly talked about by many people. Apart from the attack line, the condition of the middle and back players is also problematic because there is no balance that can give the team victory.
It's different because Real Madrid has good finances and they can buy finished players without having to wait for players to be promoted. Barcelona is experiencing financial difficulties and this cannot be done by them so whether they want to or not they rely on young players who have just received promotion.