Rarst already said the main and obvious rebuttal to this article above so I'll try and avoid repeating it completely. As the author of Bedrock (which is "total site dependency management" in your words), I made it specifically for developer-driven sites. It's not meant for freelances to crank out a WP in 1 day and then hand it off to the client. Any developer can still do that if they want. It's just not the focus of the project.

There's also 2 statements made in this article that are simply wrong:

1. "WordPress’ focus on end-user ease-of-use — just jump into the admin area and search for a plugin on the WordPress.org repository, or upload the Zip archive you got from the seller — doesn’t work when you’ve used Composer as your way to install WordPress."

2. "WordPress core’s hard-won auto-patching is disabled when you’re using WordPress as installed by Composer."

Using Composer does nothing to stop/prevent/disable the above functionality.

Anyone can use Composer to install WP core/plugins AND still be able to update/install either from the admin. Which is why if a developer wants to start a site with Composer and then hand it off to the client, it will work exactly as a normal WP install would (provided they include all the package sources along with it).

I hesitate to put much stock into this article when such glaring mistakes were said as facts.