I'll try to debunk this useless perception that Messi has poor movement and walks a lot because he is disinterested or lazy.
From playing experience as a striker, I can tell you that one of the most important aspects of playing the position is fitness and form. More so than any other position on the field, the striker needs to be fit, healthy and fresh.
Rule of thumb for any level of football: An unfit striker is an ineffective striker, and a tired striker is a useless striker.
The more tired you are, the clumsier your touches are, the slower your thinking is, and the poorer your shots become. In any other part of the field, this issue becomes lessened because you have more space and/or more time, like in midfield, or you just have to destroy and control, like in defense.
Only as a striker, are these issues so influential and crippling. The striker needs to have the best touches, needs to think the fastest, and needs to shoot truer than any other player. Tiredness and lack of fitness are utterly devastating.
Messi does not press like the rest and does not run like the rest, however, Messi also scores more than the rest.
Messi saves himself, so that he is fresh to have the perfect touch, thinking lightning quick, and shoot with uncanny precision.
There is a reason that through the years as Messi has transitioned to the CF spot, he has moved less, pressed less, but scored more and more.