Lionel Messi's return to Barcelona is a deal I never wanted materialize and I'm glad it didn't working, Barcelona would have taken step backwards if Lionel Messi had return to Barcelona because the team would have returned to Messi reliance yet again and it would have been a problem whenever he's retiring or quitting football generally.
And Barcelona-Messi didn't work out not because of FFP regulations, Lionel Messi was a free agent and so there wouldn't have been any signing fee, but his wages is not something Barcelona can afford according to La Liga rules, so it would have been impossible for Barcelona to register him in accordance to La Liga restrictions and rules.
I think Barca were keeping everything in check and lot of old players were making the move and some of them taking a deep salary cut to make space for Messi. Barca were also keeping things in check with LaLiga and LaLiga did give them
green light with the move and which is why meeting between club representatives and Jorge Messi happened in June. But in the end,
Messi made the decision to not to move to Barca and in his video he did explained that he don't want to be the reason and even if he moves to the club it will be hard for him to leave the club later on if thing goes again to same situation. I would say his wages and his moves wasn't much of an issue from Barca's end as they were carefully checking everything but it was Messi who made the decision.
There were lot of mixed expressions about Messi to Barca potential move but in the end it didn't happened is what happened. I personally wanted to see him in Barca back again but I feel Messi also made the right decision.