You are kind of right, they spent lots of money last season getting players, but its not all about having big squad but the players should be ready to work for the club. See the way Arsenal performed well last season and most of the players in the club are young player, but from their performance, you will see that those players are ready to play for the club. I think Chelsea needs young and talented players, its not all about getting big players, but getting players that are ready to play for the club.
They have spent a lot of money to get quality players but still in the end there is no change they can get. In my opinion the players have worked hard according to their respective qualities and what is the problem in my opinion personally is from management who lacks attention and cannot give freedom to the coach, they just play and cannot work well together on the field so that team cohesiveness is difficult created.
Right from beginning i knew Chelsea's, problem is not from the coach but from the squad, Tuchel was a talented coach, and since they sacked him, things have being getting worst for Chelsea, but lets hope we see a positive result from Chelsea with their new coach.
Yes, it's a shame, I think that at that time the Chelsea management had not sacked Tuchel from his coaching chair maybe the situation would not be as bad as it is now and we can see how Bayern Munich are now, they are successful in the Bundesliga.
From my own point of view is that Chelsea poor performance last season can be attributed to lack of team work in the squad because many of players are newly signed it take time before the team would be cohesive enough to get good results and become formidable, it has nothing to do with how good their manager is, Arsenal had one or two newly signed players Gabriel Jesus and Zinchenko integrated into an already balance squad with team work that was why the team was very formidable throughout last season except towards the end of the season, now that Pochettino is in charge I believe he start a rebuilding process to reposition the team with young players as a bulk of the squad.