I'm so adamant towards both characters, because it's a bloody eye sore that Fire Emblem is going to be catering to the lowest denominator possible instead of trying to branch out and try something new. Fire Emblem is like Pokemon where it caters to many different types of abilities, but unlike Pokemon it didn't reach that potential, and we're going to get a character that emphasizes that stigma more. I don't want the series to be known as the franchise that provides nothing but blue hair and swords.
I can't say I don't see the point in how aesthetically it's disappointing to have just blue-haired swordsman representing a series when many other options exists, it's kind of like how Metroid is mostly represented by lava stages while so many other environments are present in that franchise. However, while aesthetically it can be seen as a bit bland that doesn't mean each of those blue-haired swordsman don't have something to stand out for themselves once we look deeper. As much as you hate the example, if you want to get technical Ike and Marth are considered "blue-haired swordsman" (simplifying it a bit yes, but people rarely make the distinction anyway so just for the sake of the argument) but the two manage to fight differently using a different style of swordplay, which made them unique and interesting despite that initial aesthetic similarity. Chrom (or Lucina) could be a similar case like this, they may have that aesthetic similarity but once you dig deeper that goes away with the moveset they have.
Not to mention I'm the type of guy that has bloody imagination. Like when people were complaining about Little Mac being dull with nothing but punches, I had to go out of my way explaining the complications of boxing and the fact that there isn't a single type of punch, but multiple ones. I've emphasized this type of explanation to the point of being philosophical. I went into detail as to why Dillon being an direct clone of Sonic wouldn't work by going into detail that their body shape isn't the same and it would deviate from Dillon's claw based combat, I explained that Dixie Kong being a copy of Diddy Kong wouldn't be possible because she lacks a tail like Diddy Kong and she primarily attacks using her hair and she lacks certain assets that Diddy has like the Rocket Barrels, and I went into details about characters having movesets inspired by outside elements from canon (Lip using plant based combat with a magical girl and cheerleader flare, Takamaru using combat inspired by martial arts like battojutsu and laijutsu, Ridley emphasizing as massive size as both a pro and con and being surprisingly potent in the air similar to Sentinel from Marvel vs. Capcom games). But when ever I see Chrom or Lucina, that motivation is struck down and I draw a blank, and I'm the type of person that detested ideas like the weapon switching and tag teaming, because I knew those ideas would suffer hard from balance problems as shown in previous installments in Super Smash Bros.
You're not the only one who can imagine different scenarios for characters, many of us have different ideas on how certain characters could be executed to differentiate themselves from others and similarly, many of us can miss the options that make other characters unique. For instance, how many of us foresaw Rosalina's mechanic? It's such a creative idea that I don't think any of us really thought of and despite the stigma behind the character's initial inclusion, it won many over. There are ways to make characters stand out using the tools they have no matter how limited they may be upon first look and Sakurai as a developer has shown quite the imagination in creating these unique movesets even from basically nothing. That's why I have a problem with the idea that Chrom
can't be made unique, the options are there and Sakurai has proven time and time again he can work with even limited options to bring forth something that's really interesting, Chrom can be an example of that. Could he be a clone? He could, but it's not a certainty either that he has to rip off another character to make himself look good.
Also, just because they can have balance problems doesn't mean that those ideas won't and shouldn't be implemented, some bring very unique and creative movesets to the table and while they do sometimes suffer they can be improved, particularly since now we have the option of patches. Either way, that's just one way of looking at how Chrom could be unique.