I would say Neymar , Ibrahimovic ,Villa are not the ones... these were the signings which gave them result. You are going a long way back in my opinion. I would say signings like Coutinho , Griezmann which were mega signings but never proved fruitful for the club so bad management in terms of new signings in/after 17-18 is what took them. Their financial status was much much better when before 17-18. Also yes covid took an impact but you gotta see were Barca the only one on which it took an impact. Yeah it proved to be beating to the wound but the real fact is that they were about to get into financial crisis eventually. I would put the majority of blame to bad management back then , covid is also one of the reasons but that was same for every club.
It's never one player that really destroys a clubs financials, it's keeping the club unprofitable or spending more than they should by their own league rules that causes it. If you keep it at a level where it's profitable and allows you to earn each year, or even lose enough to abide the rules, then there shouldn't really be a problem.
I personally believe that we should be focusing a bit more on not a single player but the system that they were buying and paying for these players. If you make X amount of money and spend X+ then it will never end well. Barceloan did this, and that is why they are in financial distress. A team that pays 1 billion to a player and then makes 1.1 billion wouldn't really be in trouble, so it is just about financials and nothing more.