So this bit is actually a reasonable technical limitation - you can't quite put granular chains of "bones" to fake the billowing effect past the waist without having diminishing returns/bugs/performance issues, but more importantly, real-time hair and cloth simulation is very taxing on performance, and this was even more true back in 2011 when all this stuff was made. Skyrim came out that same year and everyone's hair looks awful in that by today's standards, and all its clothing tends to share the same basic designs (eg heavy armors, light armors, robes, clothing) to hide the limitations of their rigging. We're just seeing it really hard right now because they decided to add a bunch of pieces with capes in Endwalker...I'm really hoping it's because they were anticipating being able to fix these limitations in the upcoming update.
I don't disagree but at the same time, 1.) cool swordplay usually requires your opponent to also have a sword, and 2.) the animators have to be careful to not make your animations too long. This game thankfully doesn't have an animation lock (eg you are actively prevented from doing another attack until the anim for the current one finishes) but at the same time it'd look hilarious, and also be a waste of resources, to make these fantastic animations that you will never see more than 1s tops of because you need to queue up your next attack. And then if you take away VFX, it doesn't quite feel like you're doing anything? It's one of the problems I have with existing attacks rn, DRG's Piercing Talon has a distinctive visual sound but "looks" weak for someone throwing a spear to kill someone, and a good amount of MNK's attacks just don't....pack a huge punch (yes you may now kill me) because they are so understated - like, I'm sure their anims are great but also I have the camera pulled back so I can see what I'm doing and I'm usually not looking at my character, so the only real way I know I'm punching something is audio cues and the stance changing.
But along those lines, it has and continues to bug the hell out of me that we just have far too many anims that don't have running variants. MCH has one in its main rotation before a certain level and SCH has several too. Literally the only class in this game that isn't running 24/7 is BLM, so why on earth are there still skill animations that have you sliding along the floor with your legs stock still?