That's pretty much how it is. In ancient times, planets would have been objects that were distinguishable from stars in ways they had the ability to differentiate from. For example, with a telescope, any object that doesn't shine like a star, that moves across the sky at a different rate than the stars, or maybe has visible rings.

Then once science found things that past science couldn't account for, they redefined what a planet was, according to its size/gravitational pull or other factors, and which Pluto didn't fit. Apparently due to Pluto's small size, it's not even a dwarf-planet, and by that measure is basically just a really big asteroid (we even know of asteroids that are bigger than Pluto).