I can't really agree with "useless".
Obviously, in a case like Amazon (for whom the sky is the limit as the COVID supplier of preference AND is the predominant supplier of cloud-based IT services to corporations) the P/E reflects forward earnings that it could....very well grow into in 2-3 years.
Regarding Tesla, As Jim Thanos likes to say, "at the end of the day, it's a car company". So that one is, yes, absurd, also yes, United (and it's competitors) are essentially wards of the state at this point.
But 93% of Americans who want to work are working, which suggests to me that these fringe outliers ought to, statistically speaking, be discounted. IOW, what would happen to the market P/E if I were to lop off the top 10% and the bottom 10% of the P/E's in the S&P 500?
That's food for thought, actually...... I may take a shot at that, if I can find a dataset to download.