Chelsea is the same as Manchester United. They need a lot of budget to build a great squad, not just about expensive players who are unable to make a good contribution. Both teams have been equally bad in recent seasons, but if they truly have a long-term project then I'm sure improvement can be expected.
If you look at Chelsea spending on players in the previous transfer market, they were very enthusiastic and the club owner had even spent a lot of money on player recruitment. But speaking of expectations, it is far from expected because even though you have spent a lot of money, it does not provide maximum results. I agree with you, that it is not a question of expensive players, but rather how the two teams can find the players they need.
That's what neither team did and they bought players who were unable to contribute to the team. I think this is something that needs to be studied and for next season the two teams must really look for the players they need, not players who have high value. Manchester United failed in many ways this season and vice versa with Chelsea, so they must try to do better next season.