LeBron passed off to Green of all people...he just isn't the guy you want with the last possession game on the line.
He's a pretty good shooter, and he was WIIIIIDE open. I actually don't have a big problem with that particular play. I know the Heat wanted to make sure someone else took the shot besides Lebron, but I doubt even they wanted to give up something quite that open.
That being said, I do think it still reflects a deficiency for Lebron that's always kept me from ranking him as the best of the best. Some of the other greats known as assassins just seem to be more deadly in last possession situations, whereas Lebron just either drives to the hole or shoots a 3. Guys like MJ, Kobe, Bird, even Magic ... in those closing seconds it just seemed like they'd always get off a pretty makeable shot one way or another.
I don't doubt that some of those other guys would have also passed in the same situation to someone really that open, but I also feel like some of those guys could have manufactured something for themselves a little better than Lebron often does. MJ and Kobe were quick enough to dribble away from double teams (or could just take and make really tough shots), Bird just knew how to get open (and if not he'd just hit one right in your face), Magic was a great late-game improvising shot maker, etc.. Lebron as great as he is, that's just not his forte. There are a number of guys who I'd pick over Lebron in a last-possession scenario.
The only arguments I see for him are silly narratives like "10 finals in 18 seasons" or "championships with three teams" as if that matters
Lots of Finals appearances isn't silly ... despite playing in a weaker East, a number of times he made it to those Finals despite supporting casts that frankly shouldn't have been good enough to get there. I also don't have a problem with his W-L record in those Finals, since many times he was not the favorite despite clearly being the best player in the series. I think he definitely added to his legacy even without winning a bunch more titles. I mean, if KD doesn't coat-tail, Lebron almost certainly wins another 1-2 titles ... it's not a knock on him that a different superstar decided to join a 70+ win opposing team.
Championships with 3 teams is a bit less meaningful, just given that free agency has made it possible. There's no doubt that some other greats could have done the same if they'd played in a league where player movement was as easy as it is now.