PopeOfChiliTown
Smash Ace
Simple, Flamethrower is a ranged attack, and you can angle it so you can trap you opponent. It will give some space.
It's far from an effective spacing tool. It's just an attack that takes up space. A real spacing tool not only takes up space, but forces patterned movement by the opponent, limits options, and allows for follow-ups. You'll agree, I hope, that flamethrower really does not do much of either one of those.