There is no such thing that raw/vanilla js is unmaintable, what is unmaintainable is stuff that breaks regulary and vanilla/raw js never(almost?) breaks.
Er, what? The language is not what is breaking here, your application is. If you try to build a complex stateful application with no frameworks, you will more than likely create an unmaintainable buggy mess. You won't be able to reliably add new features without breaking something else.