Hello!
I aim for an amount of realism roughly equivalent to vanilla Factorio, often a nudge toward more realistic simply since with more ingredients there is opportunity for that nudge.
Personally, I treat the setting of vanilla factorio as a sort of super-high-tech stranding situation. For example, I decided on the aluminum mini-overhaul because indeed, as an engineer with hand-held supertools and item-devouring "labs" that can re-derive details of technology for you, you might treat something like aluminum as a less valuable resource than some others.
I totally understand your hesitance around these types of realism. I've sort of had to balance between realism and gameplay frequently.
I suppose, specifically for things like aluminum, one way to imagine it is that the engineer is able to collect very small quantities of various metal oxides and such to create thermite-like reactions for smelting. Perhaps the "coal" on this planet is able to create a superhot reactions itself due to geology and ancient biology. Maybe the atmosphere contributes to it. Who knows :)
Though it is indeed an overhaul, I think IR2 does a pretty good job of getting close to a more historically accurate order. And for an even bigger overhaul, Pyanodons does a pretty good job of using different techniques for smelting, and allows for things like arc furnaces pretty early in the overall tech tree.
My mods will probably not, on their own, diverge from vanilla as far as those do.
