> The frequency doesn't make the criticism more valid (...)

The criticism is not valid. It's specious reasoning at best, fueled by a hefty dose of gatekeeing.

The only rationale that is relevant is whether the standard library provides a way to do a very basic and fundamental task instead of having to force anyone to onboard and manage third party dependencies. That's the whole point of a standard library, isn't it?

No the point of a standard library is to provide vocabulary types (so that third-party libraries can interoperate) as well as basic operations that are essentially set in stone. Anything beyond that needs to have its usefulness weighted against its maintenance burden, which for a standard library that is serious about backwards compatibility is enormous. C++ is already also heavily criticized for being complex with many problems having multiple outdated solutions that you're not supposed to use.

"Onboarding" a third party library isn't this herculean task that you make it out to be but is in fact a very basic part of software development that almost any project will have to deal with anyway unless you are into reinventing the wheel - even excessively bloated standard libraries don't manage to cover everything.