Intended! I want this game to be really open in terms of what you can do with combos, but there's multiple things that scale as a combo gets longer. Damage gets lower, the opponent is pushed further away, and launchers don't launch the opponent as high. At some point, it'll be impossible to hit the opponent with one more attack.
If that's not enough, the player getting hit can escape combos by pressing the dash button, as long as they have a bit of meter. This is punishable if they do it blindly too, but with good timing, after the right kind of attack, they can even turn things around to land an attack of their own.