I think seperating the fanboyism from the objective discussion of where Messi stands on the all-time podium is becoming more interesting and complex as he ages. Those that pop up in here after any good performance and declare: 'GOAT' don't really aid constructive discussion - especially so as they don't say a word after performances like the Juve game - but a few elements regarding Messi are undeniably forging themselves in his body of work now that could only be proven over time.
29 is an age where the other two who are probably his only competition at the very, very top gave their last hurrahs. After that, they were no longer a patch on their former selves and it could be fairly said that younger stars began to shine brighter than either of them (Mueller, Beckenbauer, Cruyff etc; Gullit, Van Basten, Baggio, etc) and that they were no longer in contention as the world's best player.
Wherever you stand on the body of work of any of the three of them before the age of 30, Messi has the chance to take longevity to another level in regards to discussion within this select group and actually leave the others in the dust in this department should he continue along his current path where he is clearly no longer at the peak of his powers but can still post up performances and stats like he has done this season into his 30's.
It seems more like a case of motivation for Messi as opposed to his body being wrecked to the point he can no longer get it to do what he wants ala what Pelé experienced by 30. There's no doubt that the horrendous fouls and hardships both Pelé and Maradona had to endure hastened their decline by a degree that might have to be factored in if Messi does continue along this season's performance output for another 2-3 or 3-4 seasons (and there's not much reason why he shouldn't outside of his own zeal) as he, and what he shows capable of would not be unfair markers for what could have been for the other two (certainly Pelé - Maradona's addiction issues are another discussion entirely) had their footballing lives at the top ended organically.
I don't know if it is the same for others with an objective curiosity about proper 'GOAT' discussions, but I am finding Messi's 'bottom-level' far more interesting than his peaks or top-end performances. Alongside Pelé, he has the best 'bottom-level' the game has yet seen, I think, and it is testament to Messi that in a season where most can agree that he does appear to be waning a bit (in comparison to himself of bygone years) that he can still be: on course to score 50 goals in a season; be the likely pichichi; be absolutely instrumental for his team and still have the capability to perform like he did last night.
I've thought for a long time now that the gulf between Messi and the next contender for current best in the world is completely on Messi and not the challengers behind him. As I said previously, his seems to be a case of motivation over anything else, and when he is motivated, he still puts in performances nobody else active can get near. Even in decline, given a predictive line for him waning and the next one (let's say Neymar) ascending, or even maintaining their best for a couple of seasons, is vast. Along those lines, unless some new all-time great player (let's say Mbappe is the real deal) emerges and immediately finds himself in BPITW discussions, Messi still has at least two years on anyone active as the best in the world, if not more, as assuming his motivation remains, it will simply be a case of others catching up when his [Messi's] body starts to fail, rather than them closing the gap of their own volition.
My own assumption is that Messi is a long way from done and that this will be a nadir for Barcelona as a season before they re-tool themselves properly over the summer and actually give him a supporting midfield and defence once again that will allow him to focus more on his own game than that of others as he has had to do throughout this season. He has one last realisitic roll of the dice for the World Cup next year, but that ship might have sailed by now, and the next question for purists will be whether his club form can match Puskas and Di Stefano's into his 30's and negate that somewhat anyway.
It will be interesting to see where Messi's career goes over the next couple of seasons. I think he is perfectly capable of usurping this one by a strong margin to the point some will say he is resurgent when really, we'll just be seeing him in a functional team once more. He's a long, long way from being done as the best player in the world. If he does manage that, we'll have witnessed the longest time at the very top any footballer has had throughout his career, which is a merit in itself that not even Maradona or Pelé can contest.