>>27692911As a deterrent, it's very effective at intimidating a crowd but it depends on how prepared the crowd is (primarily if they have improvised shielding or Molotovs) and how much collateral property destruction you're willing to tolerate.
Fire (more so when it's accelerated with fuel) is a very uncontrollable thing if you don't take measures to snuff them out after the initial ignition. In close quarters you might end up lighting up things that you don't want to burn, and that can lead to entire buildings or blocks being leveled or you getting caught in flames that you started.
There's a reason these things are only effective in surprise strikes at encampments in battle or scorch earth tactics. They are destructive, but are equally dangerous to yourself if handled haphazardly or in an openly dangerous environment.