Sorry if that came across as harsh; but as an accessibility consultant these issues are what I see screwing over client after client. Worse, these client's existing "developers" defend such bad practices tooth and nail because "but that's what I was taught".
It's the same reason that trash like W3schools suckers nubes and rubes year after year with their endless stream BS and bad practices.
IF the fundamentals aren't taught at the start, it's only all that much harder to teach them later on. Again, SEMANTIC markup. Logical document structure, separation of concerns, accessible metrics and contrasts.
The basics. When someone learns from a article like yours it is VERY hard to get them to unlearn those bad practices. Mostly thanks to a mix of confirmation bias, survivorship bias, and cognitive dissonance.