There are efforts to unify OOP to be compatible across codebases: https://github.com/bartbes/Class-Commons, but yeah I agree it is still somewhat of an issue.

For the beginners thing: most beginners who use Lua don't even touch OOP. The main idea for Lua is to have concepts that are super easy for a layman to fit in their head; OOP is like this huge convoluted "idea" that has a bunch of different possible implementations and approaches.

Plus... setting up the userscript/metatable structure goes a long way in abstracting it for beginners; look at how Garry's Mod does it for in-game weapons. It doesn't even use full OOP, all it has is inheritance and it doesn't even call it that; opting to call superclasses the "base" weapon. It was easy enough for me as a 12 year old non-programmer to grasp.

Plus... seeing words like "class" or "constructor" would for sure deter beginners. It's not expressive enough. When I started out, I remember looking at the curly braces for a table and thinking it was some advanced programmer stuff, and I avoided it as much as possible. That feeling would probably be 10x for something like full-blown OOP.

Once you force them to leave the editor to learn some concept on Wikipedia, you lost IMO.

I agree with you on the optimization/syntax thing, but I think it's a necessary tradeoff. Any feature that is built into the language can get some sort of buff from that sort of stuff. I just don't think the pros outweigh the cons... Lua isn't the kind of language to leverage OOP much (other than inheritance).

For me, this is pretty much the extent of OOP I've needed in Lua (along with transparent encapsulation, but I cut that code out because it would add around 10-15 more lines):

    OBJECT = {}

    function OBJECT:new()
        local obj = {}
        setmetatable(obj, {__index = self})
        return obj
    end

    local subclass = OBJECT:new()

This, combined with tables and closures, has suited me just fine.