Messi isn't the only person bearing the blames. Neymar and Mbappe are also doing the same. More blames will be coming because myself I also blame them. Messi's case is different, this is because, at his age, we ain't expecting many extraordinary things from him like He always does when in Barcelona. Secondly, Messi is doing his best to make sure that his younger stars/ Colleagues ( Mbappe and Neymar) receive enough assistance and supports that they deserve from him, with this, much is done by Messi but little will be seen. So as a significant figure, you can't escape such blames.
PSG win and lose as a team and no single person should be blamed for their success or failure in a season. Messi, Neymar, Mbappe are their attacking players who are mostly responsible to score goals for PSG and partially contribute to their winning chance. However they are not god and can not bring PSG to winning in all matches if they don't have support from midfielders and defenders.
In return, midfielders and defenders need support and contributions from those players in defensive efforts which will help them to reduce pressure on their defense system and goalkeeper. Generally, their players must do attacking or defensive task as a whole team not as a single player.
I think it is purely a desire for him to go and not because of competition or anything else because Lionel Messi has won every title in his football career. messi is often associated with mbappe and they are often compared unfairly in comparing the qualities of the two. I even think it's lucky for Mbappe to have the experience of playing with a football legend in mastering all the ways and forms in terms of the qualities that Lionel Messi has.
Messi looks to obsessed with his ambition to win another and last Champions League in his career. Beyond that, he has nothing more to want and it is not bad if he leaves Europe and move to Saudi Arabia to enjoy very last seasons in his career but be able to fill up his pocket with hundreds of million dollar.
I think Barcelona will make every effort to repatriate Lionel Messi, especially the option of selling players that they will carry out in the transfer season window to balance their expenses.
Chance to win Champions League with Barcelona is small and they are not able to pay high salary for Messi. It pluses with bad treatment they gave to Messi two years ago, they will not have chance to convince him to return.