[Grustaf]

> An accent is simply someone applying the rules of pronunciation from one language to another.

Exactly, and that is the wrong way to speak the "another" language. The ears of native speakers are tuned to a certain pronunciation, any departures from that will be harder to understand, it will be a distraction.

You might not like it, but that's how it is.

> Many regional accents from the UK are difficult to understand because they use non standard grammar, sentence structure and place stress and intonation differently.

True. It's also true that many regional or working class accents in the UK will impair your job prospects in the UK. It's probably better to come with a Swiss or Norwegian accent than a Geordie one, when applying for a job at Goldman.