Not at all. There are a lot of frameworks that support static exports and/or pre-rendering. Often those produce incredibly fast results, in many cases faster than hand rolled solutions.
If you use a CMS you have already a templating situation and dynamic content, using a framework, or jamstack like situation is not that different, depending on the specifics it might produce faster results.
I think otherwise. I.e.: blog shouldn't be web app just because it's content management is.