I can't say if Chelsea has improved in their performance or not, it's when the new season starts is when we would know. However, their performance in CWC is impressive and their fate will be tested in the finals when they play against PSG who have destroyed and humiliated top big clubs in various leagues in recent times.
The season haven’t started yet, so we can’t conclude yet that Chelsea performance has improved, but even as they have been playing against weaker teams in the FIFA club world club, I can see that Chelsea performance has improved a little bit. The Chelsea which I know few seasons ago, even when playing against weaker teams, their performance is always poor, but with Chelsea players are now having confidence when playing, not like before that we are going to see them making mistakes.