I really disagree, with all of that. If that were the case, I'd be worried about KoF, since HD combos "look" more intimidating than JGs ever could. Or 1-frame links in SF4, Juggles in Tekken. Parries in 3s.
I really disagree with anybody who thinks SxT would take away competitive players from SC5. But I think that game looks like garbage on CFJ levels.
People can activate HD mode into Neomax, or at least Dream Cancel though. They can do something. 1f links in SF4 could be lucked into, as could 3S parries. Juggles in tekken, I think The Tekken team came up with a genius idea in Bound: they pretty much split combos into two parts, making it easier to learn.
With JG, I think people realize that it's just one of those things that they can't really do well. You can't luck into it. People are ok with mechanics they can luck into, when it becomes an all-or-nothing, they get depressed. Note: I'm not talking about your top tier players, I'm talking about the pot monsters that drive the competitive scene. You need losers for the winners to win something.
That said, I think it's possible JG never takes off at high-level. It's high-risk, and good players will throw enough (I don't think SC players are used to throws being good yet) and use delay enough that I suspect the risk-reward will potentially keep JG super-rare. I'd feel more confident about this is the movelists were larger though, and I still think it's a bad mechanic.
BTW, I think SFvsTK is going to be shit also, but it will do well. The sponsored players are going to be forced into playing it by their sponsors, and I suspect that will drive others into joining suit, even if many aren't enthused themselves.
The Soul community will keep SC5 alive though, just like they did with 4.