There are two discussions running concurrently here with some conflating flashpoints.
The one discussion about the literal greatest players of all time, and the other about how poor or old Barcelona are.
It was said all throughout the build up in the game thread that Barcelona were technically superior to Liverpool and would play them off the park - those who said Liverpool's energy and vastly superior fitness would be a crucial component in the tie not being given the benefit of the doubt. Now, post tie, Barcelona as a team aren't good enough ergo, Messi is absolved, supposedly. This is par for the course with the double talk afforded to Messi perhaps more than any other player I've known.
I habour no grudge against the player - he's a phenomenal talent and a joy to watch, but, if one is to throw his name into the mix as the de facto best player of literally all time, every piece of scrutiny and objective analysis will be heaped upon him just as it was for all in that grouping. Double talk, cognitive dissonance or the simple tendancy of glossing over every one of these capitulations will not cut it.
Messi looked like a man on a mission in the first leg, a true impression of a player with the kind of character associated with the others in his tier. By contrast, he looked like someone going down with the ship very early in the second half yesterday, and not for the first time (by a long shot) which is wholly atypical of the associative banding he placed in. You cannot praise the first leg whilst flippantly dismissing the second, where he looked equally off his game contrasted to just one game prior. Like it or not, there is a pattern forming and this is happening too many times. Again, it's not about winning or losing, it's about capitulating or wilting when the chips are truly against the team; it can only happen so many times before it is a distinguished character flaw. Once the dust settles, this game, in isolation, won't do much damage to his legacy, but allied to the rest of the times this has happened, and the fact time is running out, it would be a sour mark and a lowpoint if this is the end for him/Barca at this level of competition.
In this upcoming final phase of his career, where he is expected to become a deeper player who supplies others, he will need the appropriate team-mates around him and he won't be expected to be some all-conqueror who can do everything by himself. Indeed, it would be unfair and unrealistic given all the others in his banding had either gone into semi-retirement or were facilitators for others by the age Messi is, even now. Then again, they didn't have access to such sports science, nutrition or medical treatment, so weighting of age can be accepted and in favour of Messi's era.
It will actually be a shame if the much needed rebuild at Barca takes long enough for Messi to decline in the interim. I think it'll also be a shame if this is the last time Barca get this far in the competition whilst Messi still has good years left in him.