If we need the term/concept of "isotope", or why we call them "elements" of the periodic table I just read this:

A nuclide is a species of an atom with a specific number of protons and neutrons in the nucleus, for example carbon-13 with 6 protons and 7 neutrons. The nuclide concept (referring to individual nuclear species) emphasizes nuclear properties over chemical properties, whereas the isotope concept (grouping all atoms of each element) emphasizes chemical over nuclear. The neutron number has large effects on nuclear properties, but its effect on chemical properties is negligible for most elements. Even in the case of the lightest elements where the ratio of neutron number to atomic number varies the most between isotopes it usually has only a small effect, although it does matter in some circumstances (for hydrogen, the lightest element, the isotope effect is large enough to strongly affect biology).

I am trying to better understand what the base level of things are. We have this nice thing called the "periodic table of elements", and we have say "carbon" which is a nice black (graphite) or clear (diamond) thing you can hold in your hand. But then there are about a dozen "isotopes" or more. Some isotopes like hydrogen are significant enough to affect biology, while most isotopes are negligible chemically (though not nuclearly, according to this wiki page).
What I don't understand is why we are calling them "elements" as these discrete things in the first place. I don't see why every "nuclide" (I guess a more modern term than isotope) is the base thing we look at in the table: a combination of protons and neutrons, that's it. Rather than saying "Carbon12" or "Carbon13", we just say "6 proton 7 neutron thing". I'd like to know why we need the concept of "elements" in the periodic table, and if it would not be better more helpful in the long run to simply think of everything as nuclides rather than elements with isotopes.
 A: As the quote explains, the effect of extra neutrons on chemical properties is usually negligible. Protons and electrons are what matter in chemistry and biology. These fields are more relevant to real life than nuclear physics is, so the concept of an element like carbon makes sense. Nuclides are basically a minor detail. For example, carbon dioxide is a greenhouse gas regardless of whether it has Carbon-12 or Carbon-13.
The reason why neutrons aren’t important in how atoms bind into molecules is that atomic structure is primarily determined by electrostatic attractive forces between the positively charged protons in the nucleus and the negatively charged electrons, and secondarily by electrostatic repulsive forces between electrons in multi-electron atoms. Neutrons, not having any electric charge, don’t exert or feel electrostatic force.
Addendum: I thank @PM2Ring for reminding me in a comment that the mass of the neutrons do affect chemical reaction rates. I was thinking mainly about molecular structure.
