We can't

[otarolgam]

False. 1.0 used Crystal Tools, the same engine SE used for FFXIII and it's sequels (and which was not up to the task of rendering a MMO world). ARR uses a custom made engine based on Luminous Engine, the engine that FFXV runs under, with some components of other off-the-shelf engines made by other companies (I believe they use features of Speedtrees and Havoc for various environment components as well.) The only things carried from 1.0 are gameplay functions necessary to support 1.0 character data being transferred in, like aspects of the Armoury System.

Wait, what? I thought the Luminous Engine was only specific to FFXV...