This has literally nothing to do with who does or doesn’t like the look of something. If I don’t like the color blue, but my girlfriend wants to paint the living room blue, that’s a totally different situation than, say, if she wanted to break down the drywall and pull out chunks of insulation.
One I don’t like the look of, the other is objectively a bad interior design choice. Creating custom options in the game where incompatible pieces are being mismatched in a way that causes idle clipping and floating pieces (and I mean idle, not just during specific animations, these pieces would be floating off the body or clipping through it 100% of the time) is a VERY poor design choice for a video game. If the game shipped like that people would be more up in arms about how lazy and incomplete the customization is and how it fundamentally fails to meet the expectation of quality set for the franchise than having the core limitation in place does now.
There is no world where a game with buggy character model assets is considered more acceptable than one where your customization is limited in a way that every piece actually fits on the model it’s designed for.
Nobody cares if you make an ugly Spartan. But Halo Infinite would be even more of a laughing stock if customizing your character didn’t at least look seamless while you’re doing it.
MCC does have a core system. Spartan and Elite IS a core system. They provide you with two base armor sets, each of which have their own unique helmets, and attachments. Halo 5 can also be argued to have a core system. You have several “cores” which is the body customizations, and then several helmets which can be equipped independently much like emblems or armor effects can be in Infinite.
Even if you want to just look at Spartans in MCC in Halo 3. The chest pieces in vanilla H3 are all attachments, not full armors like H4, they are pieces placed on top of the default chest piece. Guess what? You can’t put any of them on top of non-Mark VI chest cores in Halo 3. You can’t put the EVA attachment on top of Draugr or Aviator, or an ODST core piece. Despite them acting exactly the same way on Mark VI as chest attachments do in Infinite.
You can’t put the alternate fur attachment for Draugr on anything else either, it’s locked to Draugr, even though it’s an attachment and not really a base armor piece. You see how this argument falls apart as soon as you apply a tiny bit of logic to it?
Infinite is the first game to both let you select a core armor set AND put attachments on them as separate options in the menu. But they haven’t changed anything about how it works from past games, except for removing the ability to mix and match different parts of the core itself from Halo 4, 2A, and MCC H3. So we sacrificed the ability to pick individual core chests, arms, legs, etc. In order to be able to apply attachments as their own separate option akin to Reach. It’s a fair trade. But expecting those attachments to be universal despite a wide range of shape variance in those core armor pieces? When even Reach didn’t let you stick whatever helmet attachment you want on whatever helmet you want? Be realistic.
You’re whining about nothing.
Colors, Visors, and Helmets can, and should be made cross core. Nothing else needs it.