I completely agree. Objectively speaking, Messi isn't just the best football player of all time, he's the single best athlete/sportsperson of all time.
What he does......it's Art in its purest essence.
All hyperbole aside, he's the best Football Player of All Time, AT THE VERY LEAST.
Having said that, FC Barcelona has LONG existed and thrived (with varying degrees of success, obviously) way before Messi ever came on the scene. Sure, there have been a significant increase in trophies with Messi but I have no doubt that if and when Messi does retire, say, 5 years from now, Barca will BUILD UPON his legacy and go on to achieve even greater heights of success. Success breeds success, and FC Barcelona will survive and thrive long after the "once in a lifetime entity that is Messi", (whom we are truly blessed and fortunate to bear witness to and admire) has hung up his boots and rode off into the sunset, as it were.