Ok mate, so you're obviously confused.
Hardcore gamer =/= online player.
Casual gamer =/= single player.
Most "casual" gamers are found on PC... because, as you have already noticed, the amount of players is bigger on PC games, so it's just a matter of simple statistics. When it comes to the skill level, sure, no console player will win against PC player... unless they use mouse and keyboard? Which is possible since quite a while now. It's not a matter of skill, but a matter of hardware. Do you really think those mythical console players do not know how to use a mouse? I'm a darn sharp-shooter when it comes to my mouse, since I've been playing starting as a 7 year old, but still I prefer my console, just because of the comfort it gives me. Which is exactly why would I play on gamepad - because it's fun. I don't need that kind of precision after 8h of work, I need fun and relax, which doesn't make me a casual. Why would you even call a casual someone who can easily go through Cuphead?
So yeah, what you say kind of makes sense, but only when related to e-sport. For me gaming is much more than that. MOBA games are relatively new, so before that it was mostly FPS, sport and fighting games, two of them played mostly on consoles. E-sport grew just recently, but there is no reason to call people who have been playing for 15 years casual gamers, just because they did not catch this online hype train.
And those "real gamers" mostly on PC, don't make me laugh. Real gamers steal their games? I do tend to think that real gamers play more games than narrow themselves down to couple of online shooters. If you have seen the horrors of This War of Mine, lost friends in Gears of War, experienced Vanishing of Ethan Carther and saved Ori and the Blind Forest, you are probably much more of a gamer than the hot chick on twitch having nice stats in some Fortnite.
When it comes to exclusives, Dark Souls was a multiplatform right from the start - on both Xbox and PS4 - so it's easier to release it on PC later on, especially since Xbox has such a PC-like architecture. It's kind of a "nothing to lose" situation, depending on how it was developed. On the other hand, there is Rockstar Games, having some beef with PC's since GTA III.
And when it comes to the discussion of consoles stopping graphical progress - why would you care as a trve hardcore gamer? It's not like you need more polygons on enemy's face to kill him. Progress made by consoles is huge in terms of minimizing hardware and dealing with heat issues. Of course they won't catch up, until they will use cloud in probably next 10 years, but it's not like consoles are blocking anything. After Xbox One X release it wasn't a big deal for many companies (Rockstar, CD Project, Turn 10) to release 4K texture package and enhancing additional modes (60FPS vs 4K). We are simply at that advanced level, it's just hard for graphics to make games as beautiful as you believe they should be, which only best companies can afford. And most of those best companies tend to create console games as well, or exclusively, like Rockstar, Santa Monica, Naughty Dog, because it's profitable.
I prefer single player games. I playe them once and once again through the different difficulty levels. Trying to complete then 100% is also a challenge.
I don't like online games and I don't like shooters, though I understand why people likes them.
I'm more the uncharted, elder scrolls gamer type.
High-five! I liked CS and Enemy Territory couple of years ago (ok, more than a decade), but I'm having much more fun in a story-driven games. I'm super happy that in terms of scenario games finally caught up and are capable of giving as a true narration, which is so much morre immersive than a movie or a book, since we can actually take part in the events. In last 3 or 4 years I became a big fan of "walking simulators", which are kind of basic adventure games, with just little true game mechanics, focused on story and graphical experience. My favourite ones are Vanishing of Ethan Carther, Firewatch and What Remains of Edith Finch.