My impression from reports I've read about all the major App Stores is that they won't put much effort into processing violation notifications or takedown requests when the publisher or developer filing the complaint doesn't have an account of their own on the store - even less when they're banned (like how Terraria's devs were) - so it could be weeks or even months and the publisher of the knock-off or pirated copy gets to keep all the money they've made provided they've transferred it out of their payment account, I think?
Those would be easy to take down due to code/asset reuse and name reuse. You don't need to be an author on the platform to file DMCA reports. Otherwise, there are already lots of actual Terraria clones by different names.
They’ll have a ridiculously strong case.
Same reason why you don't see knock offs on Playstation - the approval process is complex, very long and pretty costly.
If you sue a behemoth like Google or Amazon, they'll likely gladly make a settlement with you that's considerably greater than the actual damages because they value the NDAs and lack-of-PR damage from the inevitable Wall St. Journal headlines...