unique_ptr is simple and and easy to use for individually managed memory. shared_ptr can dramatically simplify some concurrent code, as well.

For arena allocated memory, you have to manage the lifetimes manually just as you would for C -- except that the arena itself can be lexically scoped, at least.

C++ is not a perfect language by any means, but destructors are not a mistake IMO. I too find having to manually "defer" cleanup annoying. I'm still interested in zig for the comptime features, though.