If you're a player, don't appropriate other cultures. Just don't. If you think you're being respectful, you're probably not. If you're not Scottish (or of Scottish extraction), don't do that bad Scottish accent. Every D&D group is overflowing with them. Don't add to the pile. If you're not Irish, don't do Lucky the Leprechaun or Bono. No one needs to hear that 39th bad Dublin accent.
Also, remember, Scotland doesn't exist in D&D. Nor Ireland. Nor Romania. Nor Germany or the Netherlands or France.
That's another things I've been struggling with. Between cultural appropriation and taboo, there's got to be a respectful middle-ground. But by saying "don't appropriate another's culture" or "don't do what isn't of your own heritage", ultimately what people hear is; "don't play anything that isn't
you". The place in-between is hard to define.
Then things get muddied further: can I do a bad Scottish accent because I've got Scottish descendants on my father's side? Can I do a
good Scottish accent even if I have no Scottish ties? Can I explore a culture that isn't mine because I want to play that Maasai-looking warrior image that I find so cool and inspiring? Or is it worse to use the image and strip it of all its culture to replace it with my own? Is it better if I play that Maasai-looking elf image that I find so cool and inspiring?
Lets get closer to home. What about a Scandinavian-looking dwarf? I'm not Scandinavian. Is a Greek-looking hoplite closer to my culture than my first-nations ancestors? I certainly have more native blood, but I know next to nothing of their culture. Could I allow myself to play a character that has traits of one or the other? Pushing further, should I allow myself to play a person of the opposite sex? I really want to say that I can, and do so respectfully, even if I'm not perfect in my representation (or lack thereof). Or is gender ok because it doesn't involve colonialism, despite the naughty word-up stuff that results from sexism? It goes deep.
Of course, Scotland, Ireland, and our world in general doesn't exist in D&D, but for those of European descent, European nations and cultures are the building blocks of medieval fantasy, if only by the way they dressed and looked, by what they built and the weapons they manufactured, and by what they achieved politically, artistically, aesthetically (not to mention Asian, Middle-Eastern, African, East European nations and cultures). Avoiding all cultural references is impossible, even if we disguise them as elvish, dwarven, tabaxi, or dragonborn cultures.
Between white-washing everything because you can't allow yourself to play anything else, and appropriate every culture to yourself willy-nilly, I believe that there is - or at least i hope there is - a place for respectful use of other people's colour, language, culture (or tidbits of it), gender, and orientation.