Capabilities help a lot if you just want to permit/deny the action. But maybe I want to know more than "can it allocate", I also want to be able to pass in an arena to make it allocate in a particular place and I might want that to be different in different parts of the code. Generics sort of help here if you want to explicitly thread your allocator all over the place like Zig but allocation is so common in normal code that ergonomically I want it to be invisible in the common case and controllable in the uncommon case
