Barcelona is a mediocre club after Messi left, there's no chance anymore for Barcelona to win either Champions League or Europa League, the best they can get is domestic league or cheese burger league. Barcelona need to sell their club to rich owner first, then they can rebuilt their club and able to compete with the top clubs.
Barcelona need to be happy if they didn't get eliminated in the quarter final match.
We can't judge Barcelona as a mediocre club when they lost Messi because after all Barcelona is a club that has a lot of achievements and even now they are still able to compete in La Liga and the European League, the problems that are happening at Barcelona at the moment can't seem to be linked to Messi because It is indeed the financial factor that caused Barcelona to lose Messi, not the other way around, if Barcelona were not experiencing bad financial problems like now then I am quite sure that Messi would still be with Barcelona and maybe he would even retire at Camp Nou.
The fact barcelona is not as good as what it used to be. Barcelona is also financiall destroyed too and winning a trophy will not change the situation. Even barcelona is only able targeting free agent players. Barcelona was able competing with other big clubs in la liga but it's often bottling it.
Barcelona is not that bad but this club is financially bankrupt. Some levers taken by the club and no change happened to the barcelona. Im not seeing this as a very important reason.
I agree with what you said about the solution to improve Barcelona at this time by switching to new ownership then maybe we will be able to see Barcelona rise again, but unfortunately the club owner and management are reluctant to sell Barcelona and prefer to solve their problems by reducing the salaries of players, management and even selling their star players to other clubs to at least cover their financial problems,With this decision from management remaining adamant, of course Barcelona is even more shackled and will only continue to decline for the next few seasons.
Barcelona was a club owned by fans. Laporta has said that he will never ever sell barcelona fans/public ownership of barcelona to the personal ownership. It is my sincere belief that Barcelona should be acquired by a billionaire, and I fully support this proposal, but it seems that is still far from happening.
There will be no change in the ownership of barcelona.