Barcelona should be looking for a center forward to be plotted as Lewandowski long term successor. Nico Williams is indeed a talented player, but his arrival might threaten Raphinha position,
Raphinha wasn't high rated before last season, though, so his performance came in as a surprise to many. Barcelona managed to pull through some part of the season without solely relying on Lewandowski. They were firing from all cylinders, so I believe they will be just fine.
The goal is to buy Nico and create a Spanish connection in the team with Yamal. This can be very beneficial in the long term.