This is going to be a little controversial, considering there are so many Wordpress developers out there. But, I think it's time to make some things clear, so the client better understands what they're getting into and why I don't use Wordpress for website development.
1. Prone to attacks
One of the main reasons I avoid Wordpress is because the server-side open-source code is accessible to the world. This means that all vulnerabilities become known quickly and regular updates are required to keep the website from getting compromised. It doesn't matter if you're a huge famous brand or not. Hackers will exploit your website to spread malware, host phishing pages or use server resources for coin-mining and similar processes.
As per this article - "more than 70% of WordPress installations are vulnerable to attacks."
I'm not saying that custom website development is free from all vulnerabilities; but its server-side source-code in not accessible to the public, making it much more difficult to be compromised.
2. Heavy on resources
Wordpress started off as a blogging platform. However, it has grown into a huge monster of a one-size-fits-all system that can theoretically be used for anything and everything. This seemingly makes it an easy choice for people who don't know better. But, consider the humongous amount of code that runs in the background, to achieve simple tasks.
It's comparable to using a plane to travel a small distance of, let's say, 10 kms. The actual time taken to do this does not make sense (think check-in lines, boarding lines, extensive and redundant systems checks, distance for take off, ascent, descent, landing, luggage lines, etc.); and so also the amount of resources required to achieve this (fuel, manpower, time, etc.). You need a vehicle better suited for this distance.
From the few Wordpress sites that are hosted on our servers by other developers, I can tell you that they use at least 10 times more CPU and memory compared to websites developed by us.
3. Complex CMS
Multiple clients who have moved from Wordpress to our simple, user-friendly Content Management System (CMS) have said that they found it very difficult to navigate and understand the CMS in Wordpress. There are functionalities and features that they never used, but cluttered the interface.
I'm not saying it's all useless. Of course, the features have their uses; but the end-client does not need them. The client is not in the web development business. A (non-tech) client friendly CMS should have just the right amount of features (in a simple format) to let them manage the content that they need to manage, without spending time learning more than required. They can better spend that time running their own businesses.
Also, when dealing with responsive websites, we need to be extra careful when modifying any part of the layout. Many Wordpress developers install page builders for ease of use. However, the client doesn't fully understand this and sometimes cause layouts to break. As a website development company in Goa, I test each layout to make sure it is perfect on all screen sizes, while developing the website. The layout is then hard-coded and the client can only change the text and image content through our CMS. This ensures that the layout cannot be modified or broken.
4. Plugins and page load time
Most people install a whole bunch of plugins for various purposes, ranging from contact forms to e-commerce systems. The more plugins you install, the more code that is output to the browser. This increases load time, which in turn affects search engine rankings, user experience, conversion and bounce rates. All this affects the value and overall ROI of your website.
Plugins are written by various coders, so you have to be careful about installing only reputable plugins. Plugins also need to be kept updated, just like the Wordpress core. As per KeyCDN, over 50% of the Wordpress vulnerabilities reported are from plugins.
You also have to watch out for plugin compatibility - installing one plugin can break another one. Installing any new plugin requires extensive testing before making any live changes. Yes, this increases maintenance costs.
Even if you don't use any plugins, a Wordpress website contains quite a bit of unnecessary code. All these issues can be avoided with a website that is built especially for you.
5. Higher long term running cost
Due to all the above reasons, you end up spending a lot of time and money on maintenance in the long run. With a custom developed website, you may pay a little more initially, but the code maintenance costs are almost zero.
You'll also outgrow a shared hosting environment quicker and will need specialized Wordpress hosting, VPS hosting or Dedicated hosting. The latter three cost quite a bit more, as compared to shared hosting.
Furthermore, a lot of website designers in Goa have little knowledge about the internal workings of Wordpress. They just install Wordpress, a theme, a bunch of plugins and throw in the client's content. They don't know or care about the unnecessary load on the server and the slow page loads.
That said, I'm sure there are Wordpress professionals who can tweak installations to be close to perfect. But that's not how it works out of the box, so for everyone else - stop swearing by Wordpress, just because the next guy is.