Casuals, amirite? Who in their right mind would play a game for fun. What a ridiculous concept. It’s like going to see a summer blockbuster in a cinema and not expecting a manifold narrative about the nature of humanity.
What about them hardcores, then? You know the type. They dig into game mechanics like nobody’s business and try to be good at what they’re doing. What silliness is this? And they can even distinguish between developer and publisher. Are they even having fun? What is the point?

Ok, jokes and friendly jabs aside, this discussion has been going on for years now, and I highly doubt it’ll change just because a guy writes an article on a website. But hey, why don’t we try to figure out what these terms even mean? It may turn out to be harder than rant thread OPs on your favourite gaming forums might realise.
There’ll be some hair-splitting along the way, but the entire topic is that anyway. Without much further ado, let’s jump in and try not to drown.

1. Go hard or go home?

To be done with this right away, we’ll briefly deal with probably the least nebulous division in this piece. Specifically: the casual and hardcore games, or in other words: the question of difficulty and complexity.
Think for a moment about what “hardcore/casual game” means to you. Do you consider how difficult the gameplay is? Or how complex are its mechanics (level structure, stat management). Or maybe it’s defined by the given game’s potential to be played in a hardcore/casual way?

git gud kit kat meme

This is the only way.

1.1 The way it’s meant to be played

Things get muddy here. Why? Because many casual games can be played hardcore and the other way round.
Look at and play some casual games long enough and they would either reveal surprising complexity (Pokemon, Marvel: Avengers Alliance, Plants vs. Zombies Heroes), or require skills in line with “real” games. Hell, even something as casual as Candy Crush Saga requires some keen eyes, and good pattern recognition/exploitation skills (also: luck, developing hazard addiction, and no access to Puzzle Quest).
On the other hand, even legitimately hardcore Devil May Cry 3 (extra hardcore in its initial Western release) has an Automatic mode for those, who heard (and experienced) how hard it was and wanted none of it. DiRT 4 has a traditional, uber-realistic Simulation difficulty for rally games veterans, but it makes no big deal out of also having a way easier Gamer difficulty at the same time. And a Joyride mode to annoy every fan of srs bzns.
Which is nice. “Play the way you want” is pretty much the reason why Arkane Studios’ games are a ton of fun. Why not apply it more broadly?

1.2 Made this way

Ah, this is easier. Some games just go the whole hog and ignore the other end of the spectrum. Can you imagine playing Dark Souls “casually”? Dying is a part of the experience, and learning through pain is a core concept. There are also roguelikes, with their permadeath, procedurally generated worlds etc. These game have no easy modes.

On the other side there are games like Everything, which are just pleasant, funny, like a casual (yeah, I know, sorry) afternoon stroll. They can sometimes be an artistic experience, take up some low-key philosophical tone, or just relax, but one way or another, there’s no hardcore line in their code.

2. Nobody’s good at everything

Another way to tackle the hardcore/casual dilemma is by considering a given person’s approach to a given game. In this sense, whether you’re a hardcore of casual player changes with every game you play.
You can be a Battlefield 1 player, ranking high, MVP in every match, the works. You know the game inside out. Pretty hardcore. And then you launch, say, XCOM 2, play one deployment at best, and even then you save scum like crazy although you play on Rookie. Sounds casual to me.
No judging, of course, nobody is good, or cares to be good, at every game. Personally, I played most of DMC3’s difficulties, enjoy XCOM:EU and XCOM 2, but give me Total War: Warhammer or Stellaris and you’ll see me pushing the difficulty down the stairs to Easy at the first chance, simply out of negligible familiarity with the genres.
And yes, there are people, who cheat in Dark Souls. Again, where’s the harm if they don’t go online? Every game with rich lore deserves to be played even by those who aren’t very good at handling combat or motion system. Some people care only for the lore and the story anyway.
Which is kind of the point. None of us have unlimited amount of time (if you do: please contact us, we could use some timey-wimey magic). If playing several games casually is the price for being hardcore in one game, where’s the disgrace in that?

And now for something completely different.

As a break from reading take a look at the video from the wonderful folks at Extra Credits. They have covered the topic to an extent on their channel in the past. As usual with their vids, it’s well worth considering.

You should check this channel when you have some time to spare, it’ll be worth your time. They cover topics ranging from animation, to narrative structures, to analysis of specific systems, and more in an accessible, friendly manner.

3. What is a the measure of a gamer?

This is the real juicy stuff. I frequently come across an opinion that a hardcore is one that not only plays games, but is also interested in the gaming industry’s workings. Meanwhile a casual just plays games, without appreciation for the industry as a whole. At it makes some sense, but as some point one realises it’s not that simple.
Where do pro gamers fall? Are they hardcore if they only care about their chosen game and being the very best, like no one ever was? What about the game journalists? They typically know about the industry more than others, but do they have enough time to bite into games deep enough to be hardcore?

Does it even actually matter?

In the end hardcore-casual isn’t a binary division. Not really. It’s a multidimensional space described by several distinct axes (as in: the plural of “axis”, not Gimli over-contributing) and any given gamer’s position isn’t even a point, but a convoluted vector.
And in the end, it doesn’t really matter. Everyone should be allowed to experience the medium in the way and scope they want. Complaining about “casuals killing gaming” makes no sense, when many games get difficulty levels with vivid names like “Nightmare” or “Path of the Damned”. Witcher 3 is too easy for you? Bump the difficulty and let other people have their own fun. As long as the option is there, nobody loses.
After all, games are supposed to be fun, right?