Why is point two phrased like that. Even if he is the best, MKLeo is still one top player. Why does it need to be stated that he is an exception? More still play Lucina. It's not an exception, it's simply a statement.Your heart's in the right place, but relying on snuck premises to make a point weakens your overall argument.
Everyone is aware that Lucina and Marth have the same frame data, safety on shield* and combo routes. Listing it out like that only serves to mislead people into thinking they've "missed" something about Marth. But here are the facts:
1) Lucina has better tournament results
2) With the exception of MKleo*, Lucina is played by more top players
3) The best player in the world dropped him, despite going out of his way to make use out of him
But even if you ignore the data, I think you're massively underselling Marth's issues at KOing overselling the effectiveness of his confirms. Matches can significantly swing in one player's favor when they build a lead, and Marth is in a terrible position since he can't force a KO. Maister had a much easier time against Marth's tilts once he (his words) "stopped jumping"