I don't see any statistics that the average user has any preference over which button to use out of the 3 examples provided. I think most users would assume buttons are supposed to look like the sites/apps they visit/use most, amazon, facebook, google, instagram, etc. If you button functions similar to those examples your users would be happy.
[EDIT] which is to say I think a lot of application design hours/$s have more to do with cargo-cult "brand styling" from the marketing department, and internal promotion of a project + personal portfolio-building and design-insider signaling than with benefits to end-user marketing, sales, or usability. It's not all useless from that perspective, obviously, but I'm very confident a lot of it is.
Wrong dichotomy. "Design" is not about the amount of eye-candy. Design is about how to make a product so that the user can use it most effectively. Making it visually appealing is an integral part of that, but only part of it.
https://en.wikipedia.org/wiki/Dieter_Rams#%22Good_design%22_...
I personally doubt users would know the word Skeuomorphic, let alone care what the button looks like.
> and I honestly do not want any of my products to perpetuate this emotion.
Why would you not want nostalgia? There are entire product brands built on taking advantage of nostalgia.
And nostalgia doesn't even imply "Hah, this is old and inferior".
Surely that's not appropriate for every brand, though? Especially if you're trying to look cutting-edge.
You can look cutting edge while taking advantage of nostalgia.
To be entirely honest, the "flat design" doesn't look "cutting-edge". It looks basic, which is because, well. It is. Intentionally so. If users don't care what your buttons look like, why spend tons of time making them look a specific style. That's just more time spent.
I'd argue that the reason it's become so prevalent, is exactly that. Less time spent designing, more time spent on features.
Have you tested this assumption, or is it simply something that you suspect? There's nothing wrong with having an opinion, but don't mistake it for an analysis!