I am a big fan of standardised English as an equaliser.
Before there was a standardised English, you could tell where somebody was raised by how they spoke and how they spelled. Since there was no standard set of spellings to refer to as correct, a person’s class of birth could be easily guessed.
The standardisation of the Queen’s English allowed the rules of the language to be set down and the culture of correct English rather than local dialects developed. So now your quality as a person could be gauged by your ability to master the admittedly complex and occasionally inconsistent but Standard and Correct rules. It was the great equaliser because anybody with a wit and will do do so could communicate in a form of English which was not only understood throughout the Empire but would allow the common man to speak and write like a prince.
This holds true today. In formal settings there is formal English. It is a language whose rules are readily available to anybody who cares to learn them. It is not elitist and it is not regional. It is a single language which, when used correctly, can communicate eloquence and education to any other person who speaks it.
Now obviously language is a fluid thing, and vernacular especially so. This is why it is good to have a standardised formal language which everybody can aspire to for formal discourse. Formal language should be the very last part of English to adapt to new norms so that there is always at least some part of the language where there is a definite “correct” way of doing things.
Once we let go of a centralised standard against which all variations are measures then we go back to linguistic tribalism.
Standardised language doesn’t marginalise people. Failure to sufficiently standardise language is what marginalises people.