In my completely amateur opinion, that is the one major reason why value investing is so much harder today. When Graham and later Buffett were executing this strategy to enormous success, most of a companies valuation could be traced back to it's assets -- excluding intellectual property. Now that IP is such a large part of valuations, it's much harder to execute this strategy because IP is inherently harder to valuate than tangible assets. And consequently, it's much more difficult to accurately access the difference between price and value.
Balance sheet metrics can still be important. Return on invested capital (ROIC) is a very popular "value" metric showing what a business can earn by investing in its business. The denominator is calculated from the balance sheet
Basically, if you are a good business with a strong moat, you will be able to invest in your business at a compounding rate. ROIC is a way to measure this
Yes, I agree! Metrics are extremely important in screening out for value stocks. What I'm saying simply is that there is no singular magical metric that can wipe out hours and hours of research. To simply list all stocks by EV/FCF ordered by cheapness will not automatically create a winning portfolio.
There's a sort of common strategy that uses EV / FCF (or something like that) as a metric for cheapness and ROIC as a metric for "good" businesses (to avoid value traps). I believe it has done pretty well