If that's your definition of "casual", then every game is "casual" and thus the term loses all meaning. I understand that everyone seems to have a differing definition of what the term "casual gaming" actually means but defining it as "games you play for the sake of playing" is far too broad and too subjective.
The exact definition of the term may be fought over but it is generally agreed upon that to define a game as "casual", it requires a certain level of "pick up and play-ness", that is, the games require no long term commitment, for any reason,to be enjoyable. As such, none of the three games you initially listed (as well as Metal Gear) qualify, because all four require some form of commitment in order get anything out of them. You need to play games like Fallout and The Witcher for hours to get anything really good out them both story and gameplay wise and games such as Metal Gear have veritable Kudzu plots that require paying attention to every cutscene and dialogue piece and finding all the hidden collectibles for them to make any sense. As such, you cannot just "pick up and play" them as you must immerse yourself in them and really experience them or else you're missing out.
By comparison, games like Civilization, Call of Duty and Overwatch can played on and off without having to worry about breaking immersion, as they lack any strong story elements or world building and as such can be just be "picked up and played".
Ergo, your definition of "casual games" as "games played solely for the purpose of fun" is inaccurate; ALL games are played largely for purpose fun, its just what kind of fun you're looking for. Do you want something you can play whenever you have free time and which require little emotional commitment or do you want a game that is going to consume your entire week and make you cry by the end of it?
Overwatch and Call of Duty are not casual. They can be played casually, but they're competitive.
It is not true that every game would be casual. NEARLY every game would be casual by my definition. The whole point of the definition is that it encompasses just about every game except as I said, games like Starcraft and CSGO which is known to be a competitive game. Competitive and Casual.
Time commitment. Difficulty. Emotional investment. Who cares?
But when a game is competitive, it's no longer just about fun.
As we are getting off topic, I feel I should not continue this argument, however I feel the need to do so as you are grammatically incorrect. You are using these words, casual and competitive, as they are exclusively defined by you.
"Casual" means "careless" or "employed irregularly", as in it is without commitment. Therefore, you should care about time, difficulty and emotional investment when defining games as "casual" or not, as casual implies a lack of these attributes.
Furthermore, you are over simplify the gaming community by dividing it into two categories of game, this so-called "casual" definition you have created based on your misuse of that particular word and "competitive", a kind of game that doesn't even EXIST. Games are not inherently "competitive" by design. Some games may be played competitively but there is no such thing as a "competitive game" in sense of which you define, i.e. a game played for the purpose of beating other players at that game and winning awards rather than for fun. There is no game on the market designed exclusively for that kind of high level competitive play. All games played in competition (Starcraft, CoD, Street Fighter, Halo, Overwatch, et cetera) have significantly larger fan bases of gamers who have no interest in playing these games for any reason other than amusement ("fun") and burning time, thus these are casual games; they may be played competitively, but they are ultimately casual games as they are primarily played in a careless or irregular fashion, thus meeting the definition of casual. Even CS:GO, possibly the closest any game comes to a dedicated competitive game, has a significant casual player base. Competitive games do not exist, only competitive players.
