A copious list of drivel advertising a lack of competence.

#1 Whatever you use to build a selfhosted website, you have to maintain it and deal with security issues. A bespoke system that you build has unknown security flaws, is hard to replace, is hard to find specialised developers for and is hard to update.

#2 Software Upgrades are constant

Of course. You can mitigate issues with upgrades. But the fact that you're using a piece of software that is actively worked on is generally a good thing. Compared to other platforms, WP gives a damn about backward compatibility though, which reduces the amount of time you spend on upgrade activities.

#3 Themes are only not awesome if you don't know what the hell you are doing and you don't know how to pick a good one. I trust an agency knows what it is doing, but in this case I guess not.

#4 Sure you can not rely on plugins, but then you have to build your own code and maintain it, test it, reinvent the wheel, all on your customer's pocket. That's not very efficient and doesn't guarantee your code will be better than the work of a community.

#5 The argument is getting even sillier now... To use software you need to have some knowledge, yes. But anyone can learn, which is the point. The alternative is you pay an agency to build something bespoke, but where does that leave you if you want to customise or change it?

And actually, serious work requires paying developers a lot of the time, no matter what route you go. WordPress developers are bountiful and compared to other specialists, charge lower rates. So the author makes another self-defeating argument.

#6 WordPress has lots of features that you may not need. But you can lock it down and add new features with greater ease than you can if you build something lean yourself. If there's a better tool, of course you use the better tool. But there's a reason most people go with WordPress, because invariably, people's needs eclipse the ability to cost-effectively expand beyond some simple initial features.

#7 What happens when your developer needs help?

Truly, this boggles my mind that anybody with a clue would say this out loud. WordPress has tons of documentation, forums, paid and unpaid professionals available for help, more than any other platform...and because it is OSS you can pretty much fix or at least identify most problems you might encounter yourself. If you are picking a platform based on access to help, WordPress is one of the best choices you can make.

#8 "WordPress does not have the corner on the SEO market, or any other cool feature."

WordPress largely covers all SEO needs. The time of gimmicky SEO tactics is largely over anyway. Now sites just need to make sure they generate the proper markup and run fast.

Bottom line

If you're going to write an article explaining why you don't use WordPress, do it right. Contrast it against what you use and highlight the benefits of what you use, but also be honest about the downsides. Case in point, a bespoke system has a whole array of disadvantages that can hurt clients. Many of the painpoints the author mentions become even worse if you build a bespoke system. It's not a good way to start a relationship with a client, by distorting the landscape that way.