As I said before, it simply wasn't well backed up, it contradicted facts and even ignored facts at times even after acknowledging them, and most of it was just rattling on about stuff that is just altogether irrelevant. For example:
1) His genetics connection between Rosalina and Peach/Mario/Luigi is completely false. One of the biggest points he used for that was his claim that Rosalina is left handed, when she is in fact, ambidextrous. He tried to deny this by saying that it can be passed off as "right hand bias", and suddenly making up the excuse that "if a character is left handed in games and is portrayed right handed in promotional renders only, it's just right hand bias. This is done because it's easier to market right handed characters".
Ignoring the fact that is complete nonsense as a theory, it doesn't even apply to Rosalina. She holds the wand in her right hand just as much as she does in her left, and also makes carefully co-ordinated motions with both across many games, proving her ambidexterity. Even his own video demonstrates this, but he accidentally included it:
2) His line of logic for saying she was born in the Mushroom Kingdom is terrible. His line of logic was that the same "tree on top of the hill" Rosalina refers to in her storybook is the same as a certain tree you can see on top of a hill in the Mushroom Kingdom, in the ending of Galaxy. However, it simply isn't. The tree from the storybook is evergreen. The one he pointed out in the ending is deciduous. They can't be the same, they are completely different.
However, this is again, a case of him ignoring a basic fact - Rosalina's home planet is the Gateway Planet (the planet Mario first wakes up on after being sent into space by Kamek). She directly says it is:
In the storybook, it's also stated that Rosalina "comes back to visit her home every 100 years" - and Rosalina does this with the Gateway Planet, as she says in that scene above (I couldn't get the GIF to last long enough to show the whole sentence, but the rest of it says "...with the Lumas every 100 years").
Furthermore, the Mario Galaxy stage in Smash Bros is set on the Gateway Planet - but it takes it a step further, and leaves it in the condition it was in over the course of Rosalina's childhood, not in the beat up state it was in the main story of Galaxy:
It has the evergreen trees from the storybook, and doesn't have the craters and large baron areas the Gateway Planet has in Galaxy.
3) He ends the theory by saying Luigi is Rosalina's father.
That is a disgusting assertion to make. Luigi actually had a small crush on Rosalina in Galaxy (he calls her cute, and at one point in the game, demands that Mario tells Rosalina that he found a Power Star for her, because he's too shy to do it himself). The photo of Luigi and Rosalina in the Mushroom Kingdom MatPat referred to is supposed to be them going on a date - in direct parallel to the photo of Mario and Peach going on a date to space.
In other words, MatPat's theory tries to suggest that Luigi has a crush on his daughter. I don't even need to tell you the problem there.
Now, people may try to claim that Luigi can't have a crush on Rosalina because he also has one on Daisy. But Daisy has never appeared in a main series game (Super Mario Land is not one), so you could technically say she is not a canon Mario character, and even if she did, there is no reason a guy can't have conflicted feelings on who he likes, or like both girls at different points in times. The fact remains that, over the course of Galaxy, Luigi had a thing for Rosalina, and I don't think Nintendo was trying to promote incest.
4) Rosalina's creator, Yoshiaki Koizumi, has already gone on record saying that Rosalina and Peach were going to be biologically related in some fashion at an early point in Rosalina's conception, but the idea was scrapped.
And if she was going to be related to Peach, she most likely would have been her sister. This is also based on the fact that, initially, Rosalina was going to be a much more of a minor, "one-level" character in Galaxy, as Miyamoto didn't want another major female character in the Mario franchise at that point. Her design, however, was much more similar to Peach in the early stages of development:
These points are not me overanalysing, they are me being aware of very basic trivia in relation to Rosalina, and knowing MatPat is wrong based on it. I'm sure if I really wanted to, I could find even more wrong with the theory. These points, however, are what I remember being wrong from when I watched the video when it came out, and didn't take any thought at all for me to figure out.
