Having worked briefly in ads targeting, a big issue you'll face is that for every whale for whom this is a massive life problem, there's a whale who is just ~rich and this is their hobby.

I actually had a colleague who was a whale. Spent about $30k/yr on mobile games. He was staff level and made like $350k, single guy, so while it was hard for me to understand, it's also hard to say he was being duped or something. He just really liked the games, liked cosmetics, and liked to "support the devs".

These whales will be pissed if you ban them. Why should they be banned from their hobby because someone else can't be personally responsible?