I've been a web developer for 10+ years and I have experience with custom building something versus using something that is templated. There are trade-offs to both and the right answer depends on what you need.
Using a template is really useful when a lot of pages are going to be the same. However, the downside is that it's a template. It will naturally have restrictions and there will always be something you will need on on off pages.
Having something custom made is more level of effort. It's harder to maintain consistency in an application and making something reusable across projects becomes more difficult. However, it does allow you more flexibility to change things on the whim without the confines of a template.
If you want to discuss a particular system in more detail, I'd be happy to have a call with you to answer your follow up questions.