And in general, people pointing at Rust "limited" stdlib (it's only limited compared to Python) as one of the big issue and risk with rust are, in my opinion, misguided. You will never make an stdlib big enough to remove the need for external dependencies. It also creates a bunch of other problems. Actually, to take Python as an example, some functionality being in the stdlib have created a bunch of issue over the years since you can't just introduce breaking changes in an stdlib as easily. Look at urllib2/3 or xml in python. In the end, almost everyone ends up using requests and lxml instead. There are many issues that need to be dealt with to mitigate supply chain attacks. A bigger stdlib or an "stdlib-extended" a la Boost, is not one of them.
Also, specifically for Rust, many people run in a no-std environment (anything sized constraint for the most part). So another stdlib would do nothing for them.