Well I did say that you could ask for reasoning and I didn't explain myself because I was tired, so no need to go on a rant. Also your last sentence: "In conclusion, I would have to mix things up anyways." WTF are you talking about there? I can't figure it out. Anyway, response time.
Your judging a character based on 1 week of playing.
I'm judging a character based on nearly 8 months of experience. I've analysed many different matchups beyond a simple pros and cons list. I play her in tournament. I know her frame data. I'm even developing tech for her. I think I have a pretty good grasp on this character.
About Luma breaking grabs, there's 2 ways that works: You input an attack but Rosalina gets grabbed, Luma still finishes his attack and breaks the grab(I can say from experience that this almost never happens). The second way is if you're holding Rosalina for way too long and you gain control of Luma again (I can say from experience that this absolutely never happens against someone good) And using Luma breaking you out of grabs as a way of saying that she's easy is just silly. She is so much more complex than that. A little gimmick that rarely plays a role in a a match does not make a character easy. I also seriously question your opinion on "easy" when you say that Fox is pick up and play. Fox is an extremely precise and technical character with a huge emphasis on positioning and matchup knowledge.
Now, why is Rosalina hard? Well, I'll get to that. One thing I have a feeling of is that you think defensive play is easy. You think zoning is easy. This paragraph will mostly be explaining how wrong of a statement that is (If you already know that zoning is difficult you could skip a bit). Zoning, and I mean actual zoning, not Link rolling around and charging arrows, is the complicated process of using hitboxes and potential hitboxes to create space while simultaneously staying unpredictable with your next option and flustering the opponent to condition them into unsafe ways of alleviating pressure that can later be capitalized on. To successfully zone, one must be aware of all his options and all the opponents options in the neutral state to correctly counter the aggressive option. These options are matchup dependent, and as such, are never universal and zoning patterns must be changed game by game, stock by stock, or even hit by hit. By definition, all characters are zoners. In layman's terms, it's much more difficult than it looks.
Now, why is Rosalina a difficult character? For one, you have to learn 3 characters to play her optimally: Rosalina with Luma, Rosalina with Luma separated, and SoRo. All 3 play differently and you must know how to play each one of them. Now imagine doing EVERYTHING described in the previous paragraph, while keeping track of the movements of a sentient being, knowing how to move him, his health, his respawn timer, and his positioning, all the while using a character that plays like absolutely nobody else, with very strange tech that has never been seen before in other smash games or fighting games in general, and requires extensive matchup knowledge to be effective and working past the effects of being tall, light, and floaty, or TLF and learning double the frame data while knowing each and every single one of Luma's quirks. Know that you're in a minority when you say she is a simple character, too.
Now it's SoRo time. Remember how I said people who think she is good are people who tend to not use her or people who don't understand her well? So you have 1 week of experience with her and think she's decent and who agrees with you?
KyroChao
does, another non Rosalina player. That's just something that I've picked up over my 8 months with the character. So how good is she? Well, SoRo is a bit like Yoshi, the more you analyze them, the worse they start looking. When you view SoRo's moveset in a vacuum, it looks good, but in practice it just doesn't mesh well. It's the reason that SoRo is about 30:70 against pretty much the whole cast. (Against rushdown characters or those whom capitalize well off mistakes like
or
the matchup is more along the lines of 15:85 and I'm NOT exaggerating to prove a point I swear). This is the reason that most top level players, including Dabuz, rank her as one of the worst characters in the game.