Its actually now standard in anti-trust law now that you actually have to show significant consumer harm. Richard Posner writting has this made the standard in Anti-Trust.

In the past it was just politics and any big company could get hit with anti-trust. Presidents routinly used anti-trust to go after their political enemies.

And if you don't use this 'pure' definition you are essentially just saying 'this is a big company'. Every single large company would be a 'monopoly' by those definition.