I'm sure std::span is great, but I like mine better :)

I find it a bit hard to justify using the STL when a single <unordered_map> include costs 250ms compile time per compile unit.

The fact that I don't have to step through this in the debugger is also a bonus:

  template <size_t _Offset, size_t _Count = dynamic_extent>
  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto subspan() const noexcept
      -> span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset> {
    static_assert(_Offset <= _Extent, "span<T, N>::subspan<Offset, Count>(): Offset out of range");
    static_assert(_Count == dynamic_extent || _Count <= _Extent - _Offset,
                  "span<T, N>::subspan<Offset, Count>(): Offset + Count out of range");

    using _ReturnType = span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset>;
    return _ReturnType{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
  }

Only if not able to do import std, or pre-compiled headers, and not using modern IDEs with "just my code" filters.

As someone that enjoys C++ since 1993, alongside other ecosystems, many pain points on using C++ complaints are self inflicted, by avoiding using modern tools.

Heck, C++ had nice .NET and Java alike frameworks, with bounds checking even, before those two systems came to exist, and nowadays all those frameworks are mostly gone with exception of Qt and C++ Builder ones, due to bias.