How much ‘vanilla’ vs framework in an enterprise setting?

Hi. I often have to debate with my boss, whether we should use frameworks or packages or stay vanilla.

I have to maintain legacy code using silverlight for example. Now I advice using more vanilla JS than different frameworks, although we are using JQuery and Bootstrap.

The young folks in our team would like to handle their job by nuget.

What is your approach? Do you ise any framework you want. Is there a screening process like 'John is a CS student and only maintenance' is a no go.