Pluto was only discovered in the 1930s. The only cultural heritage of Pluto as a ‘planet’ is a few decades of science schoolbooks, but going by these comments you'd think it's been in the same list as Jupiter since the Babylonians.
1. Yes, there are culturally significant things that have happened since the 1930s, including the discovery of Pluto and its designation as being a planet. In fact, in 2006 -- far more recently -- a group of people got together -- known as the IAU -- and they also performed a cultural act amongst themselves when they decided to stop calling Pluto a planet, undertaking a social process ("voting") in adopting criteria for doing so.
2. If you would rather define a planet as a wandering star that's visible to unaided humans in the night sky, I'd respect that, and I kind of like the idea. It's somewhat romantic, and it avoids the myriad issues that the article here discusses that have caused the 2006 IAU definition to start to smell bad. However, it's really none of my business. The problem comes up when you police what other people call things, not when you decide to subscribe to the IAU of your own volition.
Because apparently sometimes between the moment I left elementary school and he went there, some dudes decided that Pluto didn't qualify as a planet after all.
Our understanding of the universe is after all quite rudimentary. How many centuries did people fantasise about forests on Venus?