Yep, definitely agree. I've started a couple sites recently and quickly found that while
I was happy just generating them with an SSG and slapping them up online, as soon as I wanted to collaborate with others the SSG had to go right out the window in favor of WordPress. It's not that SSGs can't be collaborative, mind you, it's that it's
far easier to give someone a limited-access login to a WP site and let them contribute articles than it is to try to teach someone who isn't a programmer how to navigate adding things to an SSG.
Consider what's needed for someone non-programmer-y to use an SSG:
* Download a copy of the repository and install the SSG tooling, then fire up the SSG in listening mode so they can see their changes.
* Write out the Markdown for their page. Oh, hope you have short-codes in place for things like images-next-to-paragraphs, info callouts, common page structures (cards, hero blocks, buttons), and so forth. If not, either they'll have to pause and get you to work with them to have them implemented, or they'll have to figure out writing the templates required. Regardless, once the bits are implemented in the site the writer has to work in the arcane short-code format markup required to include them.
* Now they've got their changes, they need to figure out how to stage them — either they need to zip up the whole working directory and send it to you to sort out, or they get to learn how to commit a pull-request to a Git repository.
I don't mind doing all of that — it's quite enjoyable to figure out, and I get the chance to structure things exactly as I like them. But trying to teach a theatre director accustomed to writing in Google Docs how to do all of that? Nope. Which then turns into, "here, I wrote this out in G-Docs — hope you can figure out how to turn that into a site page!".
I really do wish there were a better competitor to WordPress, something that offered the ability to lift the hood and customize more easily. There are some CMS front-ends to SSGs, but the last I checked they either were more "CMS" in the sense of "put stuff in database and this will render it" or they still weren't particularly user-friendly (or were abandoned).