Simpler metric that we have been asking startups is: money earned/money spent and revenue earned/money spent. My team looks at this number on a M-o-M and when possible Y-o-Y basis when possible.
I agree with you on LTV and CAC – the ratio in most cases is a number you rely on for absence of any other number. Regardless of how calculation varies from startup to startup and sector to sector.
We have tried to bring this to fore. But then again, it’s a non-tech person trying to figure tech business. Glad you, someone who has been in industry for so long, are trying to bring to attention the fallacy here.