std::visit, with the need for user-defined overloaded operators to be remotely useful, is frankly horrible.
A clean way to convert a enum class to the string representation of the values would be nice. (I mostly want this to make python interfaces nicer. Having to hand roll switch-cases for every enum class I'm passing through an interface is annoying)
std::pair is nice with val.first, val.second. std::get<n>(tup) is gross. Why doesn't std::tuple support first, second, third ... ninth at least?
I'd imagine the lion's share of std::tuple usage is for tuples with less then nine items.
I regularly need a fifo, with configurable overwriting semantics and conversion to more conventional types (std::vector, etc...). It'd be nice to not need to continuously reimplemented it.
std::array has a fill(TYPE) member. Why the fuck doesn't std::vector (and most general container type, really). If it's a container type, it should support variable.fill(TYPE& val);