A content management system can cost you performance as it has to "fetch" your content from a database and integrate/insert the content with your template and any plugins you are using. This costs time and hence reduces the performance of your site.
There are also security concerns. While no site is safe from hackers trying to break in popular content management systems get targeted regularly.
An alternative is to use a system to create a static site. If your site is not updated too frequently or you have the skills to update manually it might be a good idea to look at a static site generator.
Continued: 10 Best Free Static Site Generator ToolsMost CMSes, as mentioned, do two things: they turn your content into HTML by combining it with your themes and templates, and then they make that HTML available as a website. A static site generator splits that process in two: the part where your content is turned into HTML happens on your own computer, giving you a folder full of HTML files. You then upload those HTML files to the web, where they are made available as a website to everybody....
...Because your website, the thing that people interact with, is simple HTML, and it is much more difficult for it to be hacked. And since the static site generator, which contains all the computer code that does the work, only runs on your own computer and is not exposed to the wider world at all, it cannot be hacked either. This means that security updates are largely unnecessary; you no longer need to be bothered with regular popups telling you to update your CMS, update your plugins, update your site...
Have you looked into static site generators?