I totally disagree with this, quoted from the Barron's article in that link you posted...
"...Contrary to the conventional wisdom that things aren’t nearly as nutty as back then,
he sees markets as riskier now.
There are parallels between the concentration of gains in the FAANG stocks— Facebook(ticker: FB), Amazon.com(AMZN), Apple(AAPL), Netflix(NFLX), and Google parent Alphabet(GOOGL)—these days with the internet stocks around the turn of the century. But what’s supposedly different this time is “today’s Technology titans are ‘real companies’ with massive revenue underpinnings—rather than page clicks and eyeballs, as during the original Technology mania,” Ramsey writes in the firm’s monthly report to clients, known simply as the Green Book to its fans for the cover color..."
The author fails to remember that back in 2000, there were no smartphones, the Internet was still the wild-west with fluid standards fighting for recognition, and hell, the "mass-market Internet" was still operating mostly on dial-up and only ~5-7 years-old at that point.
Here we are almost 20 years later, and the Internet is way more evolved since those "heady days". That is why they were "heady", because it was all so new, so unknown to people. Those days were the very definition of the term. The FAANG companies today are far from "heady". We have a whole generation of people now who grew up with these companies from birth, and consider it par for the course, "just the way of things." It has become normalized. Remember, this all happened because of the rapid expansion of broadband Internet across the world. Without broadband, NONE of this would have been possible.
Not to mention... The original "technology mania" may have been driven by "page clicks and eyeballs", but now companies like Google have invested infrastructure in, and are profiting greatly from, new technologies that were not around back in those days, like cloud computing and storage, thanks to broadband that has now become way more affordable and made sense for businesses to adopt. Stuff like that is huge now.