Wow thanks! You're so nice!
Guess what? You're not the only member of this fandom. There are going to be people who disagree with you and who's to say they're always wrong and you're always right?
I've posted countless walls of text explaining my criticism for alicorn Twilight. But apparently you want another so here goes!
As a princess, Twilight will spend the majority of her time doing her royal duties or simply adjusting to being a princess (we've already seen plenty of these overly cutesy time wasters in MMC and EQG alone). Never mind that her friends are supposed to be in this with her (after all, they're the real source of Twilight's power, aren't they?) , we will for the most part see little more than Twilight doing cheesy gags with her wings. Oh, wait a second, did I tell you that Rainbow Dash just got accepted into the Wonderbolt Academy? Oh well, who cares! We wanna see Twilie learn to fly! What's that? Rarity met a nice stallion who could help her get recognized in the fashion industry? Oh please! Gimme a break! We'd all rather see Twilight flirting with Flash Sentry! What now? Applejack and her family are trying to get enough water to keep their stock alive through a drought? Tch! Puh-leeze! I think I speak for everypony when I say that I'd rather see Twilight attend boring banquets and drink tea! Oh, by the way, Pinkie Pie is entering a cupcake making contest but there's been rumors of food poisoning going on recently. So What? Twilight signing a pile of certified documents is way more intriguing! Hey, is that Fluttershy? Is she being burdened with the task of taking care of some dangerous animals? Aw no bother! Twilight looks so cute in her dress and she's obviously way more interesting than those lame sideki-err I mean her friends!
"But wait!", you say. "Twilight won't be leaving her friends! She'll be staying in Ponyville with the rest of them!" Okay, fair enough. But that only raises even more concerns. If she continues to be the "same adorkable pony", staying in her library, then her coronation was all for naught. After all, what's the point of having a princess when she does nothing more than what a normal citizen would do? Isn't that kinda missing the point? If she's a princess, then she is burdened with the task of being a leader. And she can't exactly do that if she's going to sit around in the Golden Oaks Library all day. Equestria wants to see a leader, not an antisocial unicorn librarian with a pointless pair of out-of-place, over-sized wings on her back.
"But it's character development. Quit being so mean to your favorite pony, Dolphanatic! Without change, nothing would ever get accomplished!" Well I, for one, beg to differ. Twilight's character was intriguing enough as is; certainly enough to get me hooked. I loved her character. I had never known a character who thought and acted just like I would in her situations, making the same decisions I would. It was a relief to see, especially in a day and age where being analytical and studious are usually shown in a negative light. Countless times I've been called out for not "acting normal" by fellow family members to the point of them thinking they must tell others in advance that I "think too literally and am hindered from socially interacting properly". Sometimes I would be blamed for not having many friends. Twilight's character was well established from the first episode, with her being the bearer of the Element of Magic. Then came Cutie Mark Chronicles which gave us a flashback that supported her storyline even further by telling us she first succeeded in passing the entrance exam for enrollment in Celestia's School for Gifted Unicorns only after seeing a sign from a future friend (Rainbow Dash's first sonic rainboom). At that point, she realized how much power she was truly capable of. So did Celestia, who offered to be her mentor to help her learn to better control her magic.
So does that add up to becoming an alicorn princess? No it doesn't. Why? Well first off, Celestia was supposed to be queen, not princess (the same goes for Luna). And while Lauren Faust said that Twilight would at some point be Celestia's successor, she probably meant Twilight would eventually work through the ranks and maybe even be promoted to princess status (with the two alicorns being queens and Twilight staying a unicorn). Maybe later she would fill in her role in some way or another as a "successor" of sorts. We don't really know. All we know is that Twilight was not intended to be an alicorn (Lauren Faust said this as well).
A lot of people (including me) will tell you that Season 3 was, in fact, rushed. After all, they had to cram a lot of would-be multiple episodes and ambitious two-parters into a measly 13 episodes. Magic Dual, along with many of Season 3's episodes, had a great buildup, only to run out of time and have an ending that was very abrupt and hard to follow. Then there's Magical Mystery Cure, which was even more ambitious. But that only backfired. One moment everypony's cutie marks are messed up (there were a lot of writing errors to originate from this alone, such as how Pinkie had no knowledge of how to work on a farm despite living in a rock farm when she was a filly, and such), the next moment Twilight suddenly ties all loose ends with almost no explanation given, in just a few verses of song. And while I'm talking about the music, let me just say this: In order to give a song the most meaning in this show, there should be time for us to let it sink in. It's hard to do that when song after song after song is being crammed and shortened just to make room for the next. It's just overwhelming. But I'm getting off track here. So as I was saying, just after everything gets solved, Twilight Sparkle, for whatever reason, finishes Starswirl's unfinished spell with a spell that she should have known from the pilot episode. Then things really go off the deep end when Twilight suddenly disappears and finds herself being promoted to an alicorn and guess what? When she reappears, she finds out that she's also a princess! Why? I honestly don't know. Because she has wings, I guess (after all, Fluttershy did say she "looked like a princess" when Twilight unfurled her new wings). This is so far from the original intention of the show that it's facepalmable. Then there's the cheesy coronation scene with Twilight eventually saying that she was "the luckiest pony in Equestria" which she certainly was, seeing that she suddenly has all of Equestria cheering for their new princess who was promoted out of the blue. In short: Yes, there were many instances in Season 3 where the writing simply fell flat.
I'd really hate to give up on this show. I'm not a quitter. I think it's foolish to be one. But on the other hand, I want to see something enjoyable. I want to see them bring back the clever story writing, the lighthearted humor, and well-rounded characters to drive it all. But right now, it all seems to slowly be crumbling. Don't get me wrong, I still love the show and there were still some good episodes in Season 3. But overall it has been a downhill slope. I don't want to put too much faith in something that may very well crush my hopes.