This is how we make progress in theoretical physics. A good example is Newton's Second Law: f = m a. A lot people think that this is some discovery about a "fundamental law of the universe," but it is actually just a definition. The net force acting on an object is defined by humans to be equal to the product of the object's mass and acceleration. You could equally create another "law" that says f2 = m v, where v is velocity and f2 is "force 2.0." Both are correct by definition, but only one is useful. If you calculate the "force 2.0" of gravity, you'll get a complex mess; whereas the "force" of gravity is an elegant equation.
Well, I would take issue with that. Sure, mathematically one can choose any set of consistent concepts and true statementes as the starting point, and treat the remainder as derived.
However, that is not how f = ma developed historically. Acceleration of course is defined as the second derivative of position with respect to time, and Galileo, before Newton, was one who contributed to the understanding of uniformly accelerated motion. Force however can be "felt" and measured independently of any motion (e.g. with a dynamometer), and well before f = ma there was allready a large consistent quantitative theory of forces without motion, that included weight ("two identical objects have twice the weight of one"), levers, pulleys, and inclined planes, buoyancy and more. So when Newton stated f = ma, he indeed discovered a law of nature.