Delves being “too rewarding” is not a problem created by delve players

Still wrong.

They are extremely trivial.

This is more wrong than your first point because it’s 3/6 heroic once per week from vault, 1/6 farmable.

This is disingenuous, because M+ awards 0.4 items per person while a delve awards 1.

Raids have a cap on running it. M+ and Delves do not have a cap on running it, but M+ is limited to a lower reward track at the end-of-dungeon compared to the vault. Also, M+ and raids both provide a challenge at rewards levels.