> Maybe businesses have tried the plaintext approach, and their business was improved by adding fonts, stylesheets, API calls, spinners, scripts, high-res images, and god knows what else.

All i can say is that I work at a small-ish multi-million dollar business that got bought by a very large multi-billion dollar business. Our site has become very, very bloated due to everything that our parent corp wants in the name of 'making things better'. I'm not saying we are stagnant, but those changes really haven't increased our bottom line in any significant way. We now spend more time and dev resources supporting a site with much more 'bullshit'. Real business decisions, ones that benefited the customer, are where real increases in value were seen.

This of course is anecdotal, but I've never really heard the opposite.