Most of the times, the sizes do not fit at all.

No doubt, every one of us has heard of the Content Management Systems that fundamentally include WordPress, Drupal, Joomla etc. which work for some relevant and appropriate applications. On the contrary, it also becomes mandatory to enlighten that, not always one get fits to the respective & relevant scenarios. 

When to consider the Customized Content Management Systems?

• Corporate Security Concerns: It helps in preparing off the unacceptable platforms. 
• Needs Advanced Features: If any website needs the advanced customization, then evaluation of the CMS platform’s limit must highly be taken into consideration. 
• One needs ownership: Developing a website with CMS open source, one doesn’t own the software. In fact, when it comes to the startups who are interested in technology’s future acquisitions sometimes also bring the licensing issues.

Alongside this, a question also hits in one’s mind that is CMS also risky?

Actually, CMS only becomes risky if you make a mistake in choosing the smart underlying technology abreast with the skilled sufficient personnel of the experts. In fact, custom software can be developed by making use of the same tools that power the reckoned systems like that of the WordPress, Drupal etc. 
The only difference is that the software would be fully customized as per the user’s usage, not assorted collectively to closely get what a person requires.