Ronaldinho had a lot of criticism in his career too, his performances in the 06' World Cup when people were waiting for something like Maradona 86', the leg vs Liverpool after our UCL title, even his performances vs Arsenal in the final or saying that he should've done more in the leg vs Milan, the one he invented an assist out of nothing.
Ronaldinho ultimately failed to get himself into the most elite of categories amongst players, who from a gifted/talent level, are peers of his. At the time of the '06 World Cup, there was no reason or excuse for Ronaldinho to not carry over his immense form and performance level to the grandest stage of all, and ultimately, he fell short where the aforementioned peers shone and further cemented their legacies - Ronaldinho vs. Maradona could've been a real discussion if the former had made the '06 World Cup his own, for example. There aren't many players in history that can have a vs. Maradona and not be laughed off as even a notion.
This doesn't detract from the essence of the player, though, as what Ronaldinho did do for those two years is always going to have its place in history for those who witnessed it; an entire club and, until(if) surpassed the most flambouyant and joyous player ever seen who actually got to the very top of the world game. These things are a lock for Ronaldinho and I'll be surprised if we see anyone surpass him as the quintessential clown prince of football, as even in the span since his retirement, individualism and expression have nosedived, and if you're not brilliant in the first place and try anything Ronaldinho-esque, you'll be booed off the pitch and/or hooked by your manager.
These players always have a bigger test when they're active, and their legend clouds our judgement as time passes, but even with that, Ronaldinho changed a club that was in his worst moment of the last 30 years and made them champions of Europe and Spain vs Los Galacticos and also won a World Cup.
As stated above, Ronaldinho's legacy is immortalised and can never be taken away from him. I don't think it's his actual legacy in question because it is fact, rather, he's now bigger than life for some because of what he embodies and what he represents. That makes him untouchable and difficult for some to objectively analyse, which, of all players to have played, I think Ronaldinho benefits from the most.
Neymar has won a treble with Barcelona and a bunch of leagues, leagues that his teams would've won anyways, and his biggest title yet comes sharing the load with the best player in the world and the best striker at that moment, maybe we shouldn't ask him to win PSG the Champions, but at least put them in the map with some solid performances and some SF/Final runs, so far he hasn't done that (I know, most of his chances got taken away by injuries). His international career so far doesn't live up to the hype, but that's not his fault, 2014 could've been his tournament until the injury, and in
2018 Courtois got in the way of him possibly making history (he was playing good so far).
I don't think that's fair on Neymar as far as Barcelona are concerned. He was a key contributor and component for one of the greatest frontlines ever seen and played a crucial role in that CL run and treble.
Neymar's legacy would be poles apart from what it is if he hadn't gone to PSG in the first place. Whatever his intention, it hasn't worked out for a myriad of reasons and there's no doubt he's looked down upon (from where he was prior to the move) for going there.
Neymar also didn't have a Ronaldo and Rivaldo in his team and had to carry Brazil far more than Ronaldinho, who, the one World Cup where he was supposed to do so, fell well short.
As I said previously, Neymar is rarely critically and objectively analysed. The cognitive dissonance is clear and he is almost certainly the worst regarded superstar I can recall for reasons other than his ability and output.
Luck takes his part in every player's legacy, but there's one thing that sets Ronaldinho and Neymar apart, 10 things really, the 10 kg that Ronaldinho has on him with both on their prime, it's easier to do what Neymar does when you're almost 10kg below the average weight/height ratio in your sport. Ronaldinho could play like Neymar with all that extra weight, that also made him more effective since it's easier to stop Neymar with physical defending than someone like Dinho, Messi or Ronaldo who, also, has shown the impact that a body transformation has in the playstyle.
Djalminha has been mentioned and he had the same problem, he was nimble and skillful, but he couldn't play physically to save his life, someone like Jesus Navas can be top 100 or 50 in the world when in top form, but if you put 10 or 15 kg on Navas and manage to get the same acceleration, pace and skillset... you probably have a top 10 player there.
I see what you're getting at, but the question for me is whether Neymar would have gotten all the same injuries as it is those that have really curtailed him. His whole game is predicated on his nimbleness and elusiveness. If he were heavier, he wouldn't have the same style nor be able to do the same things. Impact absorption and perhaps tolerance to physical buffeting may or may not improve, but who is to say? I guess, at heavier weights, he wouldn't go flying at the slightest touch at pace and injuries like he endured at the World Cup mightn't have materialised, but it may also mean he'd just get nailed even harder, resultant in the same outcomes.
Luck, as you say, plays a vital role in the destiny of these kind of players, and I think it's that, over more mass etc. that Neymar has been bereft of. The guy plays the same way all season long, perfectly fine and well, racking up numbers and performances, getting fouled incessently, but come latter stage of Cups, and the same hits he's received all season suddenly have him out for the rest of the season. Excusing the pun, he can't catch a break.
It was 2003, Scholsey, 2003!