I feel like what still needs to be studied, but which is significantly more difficult to quantify, is the long-term impact of AI-assisted or AI-generated code when it comes time to debug a production problem. Going from observed symptoms to finding a subtle bug is a task that is made much more tractable by intimate experience with the code in question.
I'm not the OP here, but I did write the blog post. I have mixed thoughts on how much should be part of std. I think that what we're seeing is a class of library where we could see a new level introduced to open languages like rust that sits somewhere above std, but is maintained and blessed by a broader group than just the nebulous community. Rust's separation of std from no-std is a good example of tiers that I think we could see evolve. Another example in the same category as clap would be serde and some of the specific serde implementations like serde-yaml that is now in a really painful unmaintained/forked status. Maybe these are things to push for more broadly in the rust community.
The argument / environment variable duality is a challenging one, especially when developing server software that should take security into account where you don't want to encourage users to put secrets into scripts. Do you end up with some items that can only be entered via one mechanism or another? Maybe that's where the fun of being a developer comes in is making those choices.
I feel like there's a sweet spot for complexity that the derive macro hits pretty well. When things get more complex it can feel like a maze, but below that complexity it's pretty nice.