I would argue there is a distinction between the prestige markers you’re talking about and the more general grammatical rules that are followed. You can use grammatically correct English without subscribing to the over complexity that is, yes, possible.

A dialect can work locally, but there is a reason why many who have travelled abroad find themselves deliberately softening their dialect and shifting closer to proper English /queen’s English / whatever we’re calling it. It’s because their dialect is hard to understand for people who are not used to it. My girlfriend always comments how my dialect comes out of the woodwork when I’m back home with family.

Saying “I be lit” or “gimme a pint guvna” just will not be understood outside of the area or cultural group that it is spoken in. Therefore for business and/or travel you need a more standard form of English that everyone can understand. That’s not some overly complex cultural dance we play to keep the powerful powerful, that’s just basic requirements of communication.