Just to clarify, MMORPGs have low graphic demands for simple reasons:
- There can be any number of players on the screen at any point in time
- Almost all MMORPGs are really old by now
Which is irrelevant to the point.
The point is, MMO's that feature body morphing, have very basic implementation of items. Whereby they are just a texture overlaid onto the model rather than a unique item.
This is primarily done as a means of optimising performance, but it also allows them to feature body morphing as it's not an issue to stretch a texture to fit (Sort of... You will still get some jank due to stretching/shrinking of the texture)
That to me doesnt imply you cannot have high quality graphics and good customization.
The conflict isn't high quality graphics and good customisation.
The conflict is with animations/item design and customisation.
Older MMO's (Like City of Heroes) could do body morphing because it used simple items, where everyone was wearing skintight suits that were simply textures on their body (Which worked well because... It was a Super Hero/Villain game so wearing skintight suits is what you're generally going for)
Other games, that use actual models for their items can not facilitate body morphing because it would end up just distorting the items (Or clipping your model through an unchanged base item). You can see this with some older games where this sort of thing happened. Instead, the way that games incorporate model differences (Such as between a singular male and female body) is by creating a unique version of the item for each model, which is of course not feasible for body morphing where you have infinite different size and shapes...
Of course, there's the other thing that can be done by certain items which is replacing your characters model with a default one when using the item. This of course disregards your actual customisation and simply forces you into a default model.
Then in regards to games with high degrees of customisation, they come with the cost of having more limited animations. Since the bones being manipulated for an animation only look correct when they're in position and customisation modifies their size and position, this causes animations to not work with customisation. You can see this in some older games where if you manipulate your character's face, all their animations break and look awful.
So yeah, you can have high quality graphics with good customisation very easily. There are plenty of games that do it. But if typically means that items (If body morphing is included) or animations will not be as good.
The better the items and animations are, then you end up with less customisation options so as to facilitate them.
It's a trade off. You have to pick which one you prefer and sacrifice the other.
