TL;DR: fix hiring (well he doesn't even say that, just "pick the right people" which sadly most of us have only some control over).
However, the author also points out training. So changing the quality of education and the culture around the people can drive this into a better direction.
Unskilled but smart is not a big problem as long es there are some more senior people. They might not get that much done, but they are still net positive :). And of course they improve if you can hold them for a longer time.
People really hard to work with on the other hand are a tough nut and can hold back projects. I think this is often bad hiring. At least a company I worked for hired because they couldn't find anyone better (for the budget) and it turned out to be a big mistake.
Either way, you have to live and calculate with what you have.
If you do product work however I don't see why deadlines are all that important and would rather focus on the small, most impactful next iteration.
It's just a drag on everyone: Nobody wants to work with that person, they fail to communicate important things, there are pointless discussions. Even honest communication, mutually agreed on workflows and so on can't always fix things.
There are definitely ways to take an agile approach to hardware development, even if you’re working with an OEM, but the outcomes look a lot more like waterfall than your typical Agile with a big A people are comfortable with. The outcome of your iterations are long specification documents (which you’ve already got feedback on from your OEM), and a lot more detail than you’d typically go into development for on the software side since it has to integrate with the actual hardware.
In fact I also mix agile with waterfall. So much easier to keep adjusting your requirements for a few milestones ahead than to scramble together stories to fill the next sprint every other week.