Middle mouse paste was great on true 3 button mice. It became a liability with the invention of the mouse wheel, which made it a total crapshoot to try to click that damn button without rolling the wheel at the same time. It’s a classic case of overloaded functionality.
Like imagine if cars put the accelerator into the steering wheel, so you had to press the steering wheel down to accelerate. Everyone would hate it and it would be a safety nightmare. We put up with things on computers that we never would in other areas of life.