There is certainly a chance that at some point, we realise a huge problem that we’ve created by doing things this way.
One thing that I think is clear though, is by using functional CSS, you can somehow keep technical debt in check. Because you’re not really writing much extra CSS as your project grows, the level of reasoning about the codebase remains very low.
There are certainly drawbacks to this methodology — but I think if your main concern is to keep the CSS codebase in check, this is a very compelling way of doing things.
I just took 2 weeks holiday with my family in Switzerland, and on my first day back at work, I was immediately “at home” in the codebase. I am pretty sure the same would happen after 3 or 6 months away from it.