Like @Wintermute, I'm struggling to follow what you're trying to say. The "better tools" you're referring to are precisely package managers. And they're useful precisely because they don't automate the decision entirely (leaving humans disempowered) but because they "help with those decisions" as you put it. So it's unclear to me where we disagree. Let me try to knock off a few things I'm not saying, just in case they weren't clear before:
a) I'm not saying we should be deploying software to production by wantonly installing whatever the latest version of our dependencies happen to be. Things like Gemfile.lock in the Ruby/Bundler world are a good idea, and my post isn't about them at all.
b) I'm not saying we should be upgrading our dependencies en masse and immediately running `git commit` without testing that the upgrade actually worked.
Upgrading dependencies will and should always be a manual process. I just want it to be less of a bottomless time-sink.
The two links I mention at the start of OP set all this background up. Perhaps I should have explicitly said people need to read/watch them before reading me. They're actually better posts written by better writers and programmers, so they're almost certain to be a better use of your time than my miniscule contribution (that I wrote without understanding Cargo, and so may well already be hopelessly wrong).