Explain your idea

It is quite annoying that the supposedly "end-game" machine that's supposed to replace my furnaces is one of the only machines that cannot be fully automated. Electrodes have to be manually inserted, meaning every 500 items I need to insert a new set.
You USED to be able to enchant the electrodes with unbreaking, which lessened the issue, but either through modpack shenanigans or Mod changes, this has been removed (as of ATM 10)

I would like if the electrodes could be automatically inserted, but, say, will overflow into the regular inventory if you attempt to automatically load too many. I don't know, I'm just a minecraft player.

Nope!
This is an intentional gameplay mechanic and will not change =)

(p.s.: electrodes being enchantable was a bug and thusly fixed!)

Forgive me if it's rude, but I'd like to hear your thought process on it? It just seems counter-intuitive to have a big, "late-game" machine with a massive glaring reason to not use it compared to it's lower-end versions. After all, in my mind, why bother with it when I can usually just automate two dozen lower-end blast furnaces and get the same result, but fully automated and about the same price?

I think it's cool to have manual maintenance in the factory. I think that's neat, I think it involves the player in the gameplay process, even towards the endgame. It means that the factory you built still requires you to occasionally do stuff for it, to keep it running. That is an attractive gameplay loop to me, and thus why I made that decision!

There is absolutely ways to stop this from breaking your automated systems too: Redstone control.
The machine interface (and even a vanilla comparator) can give you information on the state of the electrodes. If they get too low, you know you need fresh ones. If they run out, you can change your automated systems to not feed the Arc Furnace until the issue has been resolved.

It's a gameplay puzzle to be solved - if you want it to be solved, that is. If you don't, you can use the myriad of other furnaces added by other mods which are faster, better and don't need maintenance.

But IE is first and foremost about the vibes, and having to do some maintenance in the workshop is a vibe that I want to be part of this mod =)