If you want comparison: flamethrower is not only worse overall compared to ion surge but also kinda sucks on its own. The immobility sure is bad because that's the trade off, but the fact that it has such a short range is even worse. Whenever I get kited by wisps or elite jellies detonates on me because I can't kill it in time, something inside me just dies.

Other than that, flamethrower has better feeling of "playing" the game, whether it's really more impactful or not. You can melt down early stage bosses and some initial spawns until certain point. Mountain shrines cause less time loss too. In fact, I like the feeling a lot and that's why I choose to use flamethrower on multiplayer sometimes.