Not many people in the Smash community has ever played a Fire Emblem game before, so I would imagine that most of the contempt for the inclusion of Fire Emblem comes from a sense of unfamiliarity. And being unfamiliar with a series with as much representatives as Fire Emblem is what gets people to believe that they're over-represented. Mario and Pokemon aren't seen this way because a large majority of the Smash community is familiar with them. Unfamiliarity is also what gets them grouped together to something simple and usually derogatory, like "anime swordfighters", which to them, justifies their disdain for the series. Simply put, the amount of hate for Fire Emblem won't dissipate unless they have only 3 representatives, each wielding a different type of weapon. I honestly don't see them reducing the numbers of the amount of Fire Emblem characters in Smash anytime soon, taking into consideration of how frequent Intelligent Systems puts out Fire Emblem products. They've even got their own card game, Cipher, and their own mobile app, Heroes, and another game on its way by Spring of next year.
But that isn't to say that I don't think that some of those arguments are valid. I actually agree with them in some cases, like Chrom and Lucina being needless clones or at least having their moveset derived from another Fire Emblem character, commonly Marth. The two definitely have enough source material to have their own moveset, but in Lucina's case, she was a last-minute addition. For Chrom, I can't possibly imagine why, but if I had to guess, it would because Chrom was a well-requested character, so his inclusion as a fighter would be more than enough for the people who wanted him in. It'd also be because he'd fit more of the semi-elegant semi-roughhouse Chrom has going on and copies off of Roy as a result, similar to how Lucina is a much more elegant fighter than her father and thus copies off of Marth. Now, about the part of Fire Emblem over-representation, as well of the over-saturation of sword characters? I kind of agree, honestly. Marth is pretty much a necessity when it comes to representing Fire Emblem, so cutting him is out of the question. Roy really isn't all that popular in the Fire Emblem community as I'm led to believe, so cutting him won't cause too many tragedies. If anything, I'd say the only reason why Roy returned for Smash 4 was because of how popular he was as a character in Smash, hence all the "Roy's our boy" chanting he had around Brawl and pre-Smash 4. Not to mention that his weapon, the Binding Blade, is breakable in FE6, so it wouldn't make that much sense to have Roy swinging it around. Ike on the other hand, I feel is needed, at least for now. He's a more heavy hitter than Marth, which I'd say is fair game, and his weapon, Ragnell, is unbreakable in FE9/10. Chrom and Lucina were the two out of three major characters in FE13, the game that many people firmly believe saved the franchise, since it's often noted that it was meant to be the final game in series. Their weapons, Chrom's Falchion, and Lucina's Parallel Falchion, are unbreakable. So for now, they have reserved spots, but I wouldn't be too surprised that they get cut in future iterations of Smash down the line in favor of more recent Fire Emblem lords. Same goes for Robin too. He was the first worldwide My Unit character, a mechanic in which would become a recurring feature in the series. He can wield both swords and tomes, differentiating him from the rest of the Fire Emblem cast, which is why Sakurai considered him over Chrom back in Smash 4. Like Chrom and Lucina, he has a reserved spot for now, but may or may not get replaced eventually, by either a future sole tome user or a dual sword-tome user. And Corrin's a combination of previous three I just mentioned, that being Chrom, Lucina, and Robin, so they might get cut soon, since their inclusion was mainly to promote their upcoming game, akin to Roy back in Melee. The problem is, there really isn't any other alternatives. It's evident that they're going to choose Lord characters, or potentially choose recurring characters like Anna or Tiki. So anybody whose death doesn't provide the player a Game Over is pretty much out. When it comes to representing the other parts of the weapon triangle, Axes and Lances, there's only two Fire Emblem Lords that can fit the bill—Ephraim from FE8 as the lance user, and Hector from FE7/6 as the axe user. But they've no redeeming qualities or characteristics that they can add to the Fire Emblem roster, aside from being token weapon users. There's also Sigurd from FE4 who can wield swords alongside lances, and Eliwood from FE7/6 as another dual sword-lance wielder in a promoted class, but they're both unlikely since they're mounted on a horse, which would make things impracticable. Going back to the argument of over-saturation of sword wielders in Smash, I think it's valid but also justifiable at the same time. Swords are unarguably the balanced weapon of trio, providing both accuracy and power, whereas axes provide more power but less accuracy, and lances provide more accuracy but less power, hence why a vast majority of the Fire Emblem Lords equip themselves with swords as their weapon of choice. In fact, the only time they don't use a sword is when they're accompanied by another Lord who uses a sword in their stead. So regarding all of what I just said, the only possible representatives I can see in the future are Celica from FE2/15, Lyn from FE7, future Fire Emblem Lords, and maybe a Fire Emblem Heroes character. Celica uses swords but can use magic as well, and Lyn's Myrmidion class allows her to be a glass cannon of sorts—she'd be quick and powerful, but would be easy to knockout in order to compensate.
TL;DR
Arguments against FE
-Too many swordfighters
-Too many FE representatives in general
My Rebuttals
-Sword users are the balanced weapon out of the weapon triangle, hence why Lords mainly use them
-The current amount of FE representatives is fine, it's just that some of them don't represent other aspects of FE when they have the potential to do so (Chrom, Lucina)
What Can Be Done For FE to Make People More Happy
-Add Celica and/or Lyn to provide more alternate playstyles as opposed to being a Marth clone/semi-clone
-Allow more Lords to be diverse in their weapon(s) of choice (dual sword/bow user, axe/staff, etc)
You know, I don't think I've ever written a post on Smashboards as long as this one before. Took me quite a while to type it up too! Let me know if there's any typos that needs fixing.