The guy who should be the undisputed best ever footballer instead will be compared more to Ronaldo than Maradona and often unfavourably. Ronaldo has the advantage of a title with Portugal (how it came about will be brushed over), will break the international goalscoring record (the fact half of them against farmers will be brushed over).
One Champions League won after 2011 at which point Barca were so far ahead of everyone and Messi still young. No titles with Argentina. No ballon d'ors post 2015 while Ronaldo has won 4 out the last 6 CL titles and a good chance of another one and a record of a CL and league title in 3 different leagues. A chance of more trophies with an excellent young Portugal team.
While Messi spends what's left of his career playing for jokers as manager and awful football teams full of old men or youngsters not quite up to it.
His legacy is trash in terms of what it should be.
His legacy is not trash in any way. He has as good of a legacy as Ronaldo, albeit structured differently (Ronaldo's is more CL based, Messi's is more La Liga based). The problem is that Ronaldo has matched his impact and his achievements with half the talent, and that is because Ronaldo is a superior athlete. And by athlete I don't mean only in the body, but also mentality, in terms of personality, drive, professionalism.
To be honest, outside of talent, Messi is not a superior football player to Cristiano Ronaldo. It's very much like Federer and Nadal. Nadal is half as talented, but matched Federer's greatness by being a superior athlete. They used to be better, but by way of hunger and perseverance, Ronaldo and Nadal closed the gap so much, that it's not there anymore.
I happen to value talent and genius factor a lot, so for me Federer and Messi will forever be a slight notch above Ronaldo and Nadal. But objectively, they don't have any edge outside aesthetics and natural talent and ability.
Messi's legacy, like Ronaldo's, is hugely impressive. It's not a perfect career, neither player has a perfect career, and both have important failures along the years, but when you are around for that long at the very top, you're bound to have failures from time to time.