This may go about as well as the theory from the late 90's that tech stocks were destined to grow so big it doesn't matter what they cost in terms of fundamentals, but here goes:
The theory in the late 20teens and 2020 is that technology is disrupting legacy operators in industry after industry, so owning a portfolio of highly leveraged incumbent firms with sunk costs in old technologies is extremely dangerous.
Internet services have dealt obsolescence to physical media industry, movie theaters, newspapers, cable, and much of the physical retail landscape. Renewable energy, electric cars, and work-from-home software/services are poised to wipe out the fossil fuel industry, ICE car industry, and office real estate - maybe some leveraged utilities too. AirBnB is killing the hotel industry, and meal delivery services may soon spawn a generation of takeout-only restaurants that out-compete their traditional peers. Name an existing industry, and there's a tech company working to undermine it. That wasn't always the case. The pace of change is quickening.
Companies like Tesla, Google, Amazon, and Apple have access to capital at costs even lower than many Western governments, and their competitors such as oil companies, broadcast media, etc. are borrowing at junk yields, steadily increasing leverage prior to their eventual bankruptcy.
Worse, most of these tech firms wait until they are mega-caps to list their stocks on public exchanges, so they are not represented in our diversified index funds until much of their explosive growth has already happened and enriched private equity firms.