Your opinion is common in language learning it seems, as most people praise a perfect accent but some get very offended by it.

I couldn't tell you why, maybe it's a feeling of lack of authenticity?

I find it impressive when someone has acquired a good accent personally since it's quite difficult to do.

I'm impressed but it's weird to compliment a non Brit on their perfect British accent when they don't sound like you, a British person...

It sounds too studied, almost a mockery of real native speakers, there's always too much of perfection in the way these learners speak that makes it sound uncanny

Interesting, yeah I can see that. A lot of modern language learning tries to get you to sound natural, but the question becomes, natural where? You start to delve into dialects, when I meet people who learned English naturally from TV and media, they often have a weird blend of dialects that constantly switches, it's kinda fun actually. One minute they have American inflections, next they're Australian etc.

When learning Japanese I was encouraged to pick a person with a dialect I prefer and listen to them a lot, as I'll likely pick up their accent and mannerisms.