Don’t get me wrong, if you have a good jam or preserves it’s totally fine on a sandwich, and I wouldn’t turn my nose up at it. However, peanut butter doesn’t really need the help, and the extra sweetness from jelly is totally unnecessary. Toasted bread and peanut butter is all you need for a quality simple sandwich.
No, a peanut butter sandwich with no peanut butter would be objectively terrible.
Proof by counterexample: I like it better
bread can be really good, and if you get good bread it’ll taste delicious on its own too. though I do of course use toppings.