Given that ref structs can now be generic arguments and cannot be boxed - you have more ways to enforce that no boxing occurs at compile-time. It is true that you have to roll your own collections, but even dispatching on interfaces by making them generic constraints (which is zero-cost) instead of boxing is a good start.
As for delete operator, 'dispose' works well enough. I have a toy native vector that I use for all sorts of one-off tasks:
// A is a shorthand for default allocator, a thin wrapper on top of malloc/realloc/free
// this allows for Zig-style allocator specialization
using var nums = (NVec<int, A>)[1, 2, 3, 4];
nums.Add(5);
...
// underlying pointer is freed at the end of the scope
This retains full compatibility with the standard library through interfaces and being convertible to Span<T>, which almost everything accepts nowadays.
System-provided allocators are slower at small allocations than GC, but Jemalloc easily fixes that.