The dye and materia System as well as 2 piece armor...

[Alhanelem]

At level 50 I have yet to find a piece of gear that will let me dye it. Also non of the Gear that drops in AK, Darklight, or AF2 has a materia socket.....

Only crafted gear can be dyed and materia'd.

Why can't Darklight and Allagan, and AF2 pieces have materia slots?

Because it would be too powerful.

Even with the ilvl70 giantsgall weapons, while they were inferior tot the primal weapons, you could stack huge amounts of your main stat by multi-melding making them FAR better than anything else. Now, each stat on an item has a cap so that's not much of a problem anymore, but you can still add a lot of stats (just not the same stat). So they still don't want it to be on the best items because it would be too good.

The rose gold accessories, which are ilvl70 and meldable (but not dyeable as there's nothing to dye really), are actually really good. but they're also insanely expensive b/c you need 9 peacock ores to make the rose gold ingot, and you can only get peacock ore by trading for them with tomestones (or buying ones that other people traded for and chose to sell)

tl;dr it's for balance reasons.

(Note: a lot of people don't realize this but multimelding is still possible like in 1.0- The slots are always 100% success rate, but you can go beyond the number of slots on the item it just has a high fail rate)

[Tupsi]

Only crafted gear can be dyed

Incorrect, I dyed my Aetherial (Pink) gear just fine.

[Pooky]

Incorrect, I dyed my Aetherial (Pink) gear just fine.

Aetherial gear is just dungeon boosted versions of crafted gear.

[Leonas]

Only crafted gear can be dyed and materia'd.

Actually, big no here.

Some green sets will let you dye them, others won't. I think its because of whether or not the set has a unique design to it.
AK's set you cannot dye. This, for monks, is called Peltist.
Palace's set on the other hand allows you to dye it, as I've done plenty of times. This set is called Siphani for monk.

And no, you can't craft them.