Eh, online definitely promotes shitty tactics or behavior, but its on you to punish those tactics and behaviors. Online mode is still the best way to constantly learn match ups, test your fundamentals, and apply training mode strategies.
If you're new to a game or type of fighter, yeah, scrubby shit that you don't have the knowledge of punishing will suck. But learning any fighting game outright is really hard.
Plus, you have to be ready for scrubby tactics in offline play as well. If you can't handle someone doing something dumb, you're gonna lose when you run into that type of person.