The problem has less to do with the frameworks chosen by the main website's developers, but rather the countless third party services which are mandated by marketing/business realities.

Think Facebook pixel, google analytics (et al), Optimizely, Mixpanel, various "widgets", etc...

In other words: you probably don't really have this problem unless you're working with a large team and for profit.

Easiest way to win these battles is to show real-life "Before"/"After" examples of your site with and without bloaty services to whomever is advocating for their importance.