The distinctions ARE important, and absolutely matter - think of WoW's Warlords of Draenor (WoD) expansion. It's near universally disliked for a number of reasons, but a big one is that the only things to do in it were really PvPing and raiding. There is that "The one thing it DID do well was..." argument, which is the raids. But that was it. Catering to one part of the community to, effectively, the disregard and cost of the entire rest caused a massive collapse in player numbers that was, at that time, unheard of for WoW.

So it very much does matter where the game has dearths of content for swaths of the playerbase.

The issue is defining what that is. Is someone who maxed out Ishgard Restoration and has the pterodactyl mount NOT hardcore? Their content didn't require a group but it required a massive time investment and probably outside of game research on efficient gathering and crafting and farming methods, gearing/food buffs, and probably macro generation. It's one of the most rare achievements in the game, though it doesn't require voice chat or scheduled game time. Hardcore fishers are a legend unto themselves.

Some people say Extremes and Savages are "midcore" while others laugh at the very idea of anything with a body check and enrage not being considered hardcore.

But I think people get lost in the weeds on that a bit. While trying to get more universal definitions for the terms isn't a bad idea, it misses the forest for the trees. The real question, and the matter to be concerned with, I think we can all see:

If the game has large swaths of the playerbase it's either not providing content to, or content that is quickly consumed and doesn't have longevity, this is a problem, especially if that's a large portion of the playerbase.