Looking flashy is a _significant_ signal that users rely on to determine if the content is quality or not. It's a sad fact that, if your site does not ape the style consensus it'll look outdated or worse like a scam. Its the same reason used car salesmen wear suits.

You’re probably right about most users, but when I see a website that doesn’t bother with CSS at all, for me that’s a strong signal of higher quality content.