> From what I've read, precisely measured ingredients are a modern invention anyway.

I believe this is where the cup measurement came from. Baking is all about ratios, so you could take any (drinking) cup you happen to have and use it to measure your various ingredients, as the ratios will all work out by using the same cup.

I recently saw a very expensive chef’s spoon that was supposed to be a perfect teaspoon(?) and had various other features. It was sold out. Out of curiosity, I went into my drawer, pulled out my normal spoons I eat with and compared them to what my measuring spoons held. It was the same. I just use my normal spoons to measure now. Good enough. I can then use the spoon to eat with, depending on what it is.