After talking to some people and reading several comments made by other users, it seems that I'm not the only one growing increasingly more annoyed with Erza's flame pants.
However, it did make me wonder: is the hatred towards the flame pants due to the way Erza's character is supposed to be, namely an armour-using character?
Could these flame pants have been great had the author put in some more effort to have Erza go through some character development?
Let me list my opinions on the flame pants and how I would've handled Erza's character development to make the flame pants accepted rather than hated by the readers.
It all started with the Erza vs Ikaruga fight. There, her armours got destroyed and she focused everything on attack while wearing those flame pants.
I can understand the logic that if defense fails, one should discard it and focus on attack (something like "offense is the best defense") and it was nice to see it happen once.
In my opinion, this fight was a turning point in Erza's development. It was during this fight that the heavily resented flame pants made their debut, but that's not all. This fight was the perfect opportunity to change Erza's fighting style altogether.
It had already been stated that Erza had a mental issue where she didn't feel comfortable when she wasn't wearing armour, even when out of battle and it was during the fight with Ikaruga that she overcame this by using nakama reasoning.
So, if she had overcome this issue and decided that armours weren't necessary anymore, it would've been a good moment to change Erza's fighting style from relying on armours to relying on different weapons to make better use of the offensive strength she undeniably has.
The change to her wearing the flame pants could in fact be a nice form of character development, if handled correctly.
If she would've evolved into a character that requips weapons instead of armour during fights, then nobody would be bothered by the flame pants.
Heck, the author could've used the same reasoning as when Erza still felt armours were necessary, only the other way around, by making her realise she can only bring out her true offensive power by discarding all defense, thus donning the flame pants.
However, the author decided to waste this opportunity, so she is still an armour user, although one who discards her armours all the time, which is simply stupid. It's like creating an archer and having him/her fight with a sword all the time, it just makes no sense.
Right now it comes across as the author being too lazy and thinking something like "I can't be bothered to draw all these armours and invent some new ones on top of that, so let's go with the flame pants EVERY SINGLE TIME."
If a bit of character development had been applied by having Erza overcome her mental hurdle and change her very perception of fighting, her character would've become more awesome instead of being reduced to what it is now.
She already has the ability to mentally control the weapons she summons and her swordsmanship... swordswomanship, whatever, is already great.
Also, all the benefits the armours have can simply be transferred to a weapon counterpart (Flame Empress Sword, Lightning Empress Spear, etc etc) or simply keep some armours to use when the situation requires it. So her actual fights would not look that different from the ones we've seen until now, they would just be evaluated in a different way had she been an offensive, weapon-oriented character rather than a defensive, armour-oriented character.
I would've been able to accept the flame pants if the main focus of Erza's fighting style had been weapons rather than armours.
Had she used special weapons rather than special armours, there might have been some more sense to certain things she has done, like blocking Kagura's Archenemy would've had more credibility if Erza also had a special sword, rather than san ordinary one.