People about Cosplay...
Coming from a movie production background, you put on the parts of your costume that would interfere with makeup – possibly rubbing on your face when donning the apparel – before you put on makeup. None of the rest of your costume should be worn until it is just before “showtime”.
And costumers (both hobbyists and professionals) should be planning for makeup application and making a costume that can be put on without having to go over the head like a T-shirt does. Aside from the fact that this is easy to make, there really isn’t a good excuse for designing a costume that ruins makeup, or alternately, has to be worn while makeup is being applied.
When judging whether something is cultural appropriation, ask first: is there a cultural double standard that praises the borrower while punishing those whose behaviors/styles are being borrowed from? If not, then the second test is to see if the thing being borrowed has religious/spiritual/historical significance the borrowers are disregarding or disrespecting for the sake of ‘cool’. Finally, does the act of borrowing reinforce stereotypes?
To answer your question, No. Cosplaying in the past hasn’t been used to marginalize, dehumanize, or stereotype the Japanese people. Cosplay has no major religious, political, or spiritual significance, even in Japan it is considered a commercial hobby. Cultural Appropriation is problematic because the hegemonic group (in the US case, white people) get praise for behaviors the group that they borrowed the practice from get penalized for (in this case, Japanese otaku). However, Japanese otaku have the same or superior status as American Cosplayers at US Conventions and English language internet. Japanese Otaku are not facing a double standard when compared to white otaku that favors White otaku.
There are some racists who may say white cosplayers look more like the anime/video game characters then Japanese cosplayer, but those types tend to be seen as racists and pariahs in most well-balanced cosplay communities. Most people tend to think the Japanese have very high quality cosplay.
You absolutely do not have to make your own costume to cosplay! Made or bought, cosplay is cosplay. Cosplay is more than making an outfit. It can include makeup, wig styling, and prop making too, besides sewing the costume. Some people, like me, style their own wigs and do their own makeup, but can’t sew or craft. Some people simply wear the costume and don’t make any of it, and that’s fine too. This cosplay elitism needs to stop, of course it isn’t wrong to buy a costume. As long as you’re having fun, you’re doing it right.