One of my biggest problems about the world that GX makes the YGO world into is that it legitimizes one of my oldest brother's* main complaints about the series as a whole-- that is, "Why the heck are they making such a damn big deal out of a card game?!"
In YGO:DM, it mostly makes sense, most of the time. In Duelist Kingdom and Battle City, they're in the midst of tournaments, both of which have enourmous stakes tied to them. In Noa's arc, it's like Noa is restricted to some sort of "game engine." During the Oriechalchos saga, the villains have a scary magical weapon they can use to FORCE people into dueling them. AFTER the Oriechalchos saga, it actually stops being so much about cards. (And the Grand Prix tournie is really just sort of a cool-down romp compared to Duelist Kingdom and Battle City, even WITH Zigfried von Shroeder hacking into KaibaCorp's computers.)
(And in YGO:TM, the card game was really mostly such a big deal because KAIBA IS INSANE. I know it, you know it, we all know it. Kaiba is not constrained by our definition of what is meaningful or meaningless because he's obsessed.)
In GX, there's some implication that there are tournaments in the big dueling leagues, but you could easily claim there aren't, because of Kaiser's depressive stage-- that is, he's mainly moping that his sponsors are leaving him, not that he's getting knocked out of tournaments left and right. This might make more sense if they had somehow made explicit that the tournaments worked on some sort of system that rewarded a high win rate instead of constant winning streaks, like professional football. Instead, they let you wonder about what exactly Kaiser talking about sponsors actually means-- and this, unfortunately, leaves open the path they seem to take for 5Ds.
I've mentioned that I enjoy 5Ds, but that doesn't mean I think it makes any sense. It's pretty clear there are no actual tournaments. Cards are treated as outright weapons, despite the fact that we have seen that nobody can summon the Seal of Oriechalchos and randomly steal souls. (And if it turns out they can, I will be distinctly annoyed.) Professional duelists don't seem to duel in tournaments at all-- show duels take place entirely due to challenges, and the living of a duelist is entirely dependant on their sponsorships. In fact, it's set up rather like professional boxing in the era of Mohammed Ali. Which is extremely wierd if you think about it too hard, which is what I'm given to doing. No matter how wrapped up in it you may get, there's still that little question of WHY? WHY does it make any sense for the police to force criminals into dueling them? WHY doesn't Yusei just whip out a pistol and shoot somebody? Why don't any of his opponents? They ARE supposedly criminals, are they not?
In DM, dueling did tend to take center stage. But regardless of how many times the Pointy Finger of Death tried to tell you otherwise, guns and other truly deadly weapons were a stark reality within that world. In the world of 5Ds, no matter how dystopian it may paint itself, the fact remains that the worst injury we've seen came about because Jack flipped over on his damn motorcycle. And he recovered from THAT pretty quickly, all things considered. (Invid wants to remind me of Goodwin's cybernetic arm. I say pfah-- that was magic.) The only people we've seen with significant ability to use magic involving cards are all signer-types. Thus, treating cards like a deadly weapon when dealing with the general populace, which does not contain a high number of signers, MAKES NO SENSE.
*When I speak of my oldest brother, incidentally, I do NOT speak of Invid. I have three brothers, and Invid is only one of them. My oldest brother is known best in the web-circles I run as "GAARDIAN," and is on an active mission to get me out of this fandom, which Invid is not. My youngest brother is younger than ME and is not known by anything on the internet, because he's only seven.