Barcelona currently depends on Messi more than Messi does on Barcelona.
You don't need to say this. It likely you underestimate Barcelona without Messi. Are you a Messi fan or a Barca fan?
There will be another player to be the successor of number 10 if Messi leaves Barcelona. And I am sure he will be as good as Messi in the future if Barcelona has more chances.
I am a fan of Real Madrid, but I have a sober view of the performance of both Real Madrid and its opponents.A player like Messi will not be in Barcelona for a long time, but in the whole world. And Barcelona is well aware of this and therefore wants to keep Messi as long as possible in the team. Both as a player and as a brand, Messi means a lot to Barcelona.