The issue is that they have substantial advantages over inserters with no meaningful downside, once unlocked.
The downside is, that they are bigger: 2x1, rather than 1x1 for an inserter, which means you'd have to rebuild the entire factory to fit them in. They likely cost more electricity ...

People are against the loader, nobody provides a reason why. "It's OP because I think it is." Please explain. To me it doesn't harm anything.

Ultimately item flow is limited by crafting speeds of assembling machines, furnaces and miners. The challenge of the game is getting these things right and ...

I'm in favor of the loader/unloader. It might be two separate items, or a single item.

Honestly, I don't see the downsides many people seem to be afraid of. Please elaborate – overpowered how? They can fill or empty a belt, ok, fine. How exactly is that overpowered? Ok, this allows for a much ...