Gelatin is a byproduct, animals aren’t being farmed specifically for their gelatin. It’s created with the leftovers from meat and leather production.

I’d want to fact check this, but my first thought is that a vegan replacement for gelatin might require more energy and be more damaging to produce (chop down habitat for farmland -> grow plant -> harvest -> turn into gelatin substitute) than using the meat leftovers.

I think this is where being an “effective” vegan is important; you might do more harm eating the substitute than consuming the byproduct. Depends on why you’re a vegan I guess, harm reduction might not be your goal.