Your examples are actually edge cases that DCF was never designed to handle.
There are lots of investments that are way more boring than Apple, Tesla, and Google, and that should be analyzed with DCF.
DCF is more for slow and steadily growing companies that might be undervalued for just a moment because of factors outside of the company's control.
Tech companies can be harder to value via DCF, because as you say, there are monumental factors that outweigh historical cash flow trends.
This is part of why Warren Buffet historically avoided tech. It is wildly unpredictable from a pure historical cash flow numbers standpoint.
DCF is not a crystal ball.
The types of questions you're talking about aren't well analyzed by DCF.
But something like the fair value of Walmart can absolutely be determined via DCF.