Oh man it cannot be emphasized strongly enough that Capcom has gotten nothing but flak for having the gall to try to be better than literally any other Japanese dev on netcode, but failing to be perfect in their first outing. Crazy kappa circle-jerk nonsense about SF5 being "literally unplayable" online, despite the fact that its netcode is merely not as good as GGPO, yet significantly better than any other fighting game to ever come out of Japan. Trying is the first step toward failure, and all that.
Incidentally, let me be another voice in here to say: hey, this game is actually really good and fun, and the online is way more active than BuT sTeAmChArTs!! Guy would lead you to believe.* I have way less trouble finding opponents online on Fantasy Strike than I do on GGXrd Rev2, and I live in Japan, where FS hasn't even been released. Mostly, if you like neutral-heavy fighting games that are fast-paced and intense, with short, powerful combos, it's absolutely worth your while to check it out. As far as I'm concerned, the streamlined controls thing is just a bonus that happens to make the game be 100% playable for real on a single joy-con.
*There is actually a genuine issue where a small but significant number of players can't get matches without forwarding ports, though. I'm holding out hopes that the devs change the ports that the game uses in an upcoming update, because it's the one and only time I've ever had to forward ports to play a game online.