It’s been a while since I’ve read much about this but one explanation I’ve heard is that Vo2 was elevated to importance because it could be accurately measured and therefore studied.

Also unlike aerobic fitness, which can be improved with year after year of consistent training, an athletes peak Vo2 max (for their given fitness) can be maxed out over 4 - 6 weeks of specific training. Doing much more specific Vo2 training can result the athlete (at least in running) becoming ‘flat’.

That said Vo2 measurement can provide a great deal of useful information but for most recreational athletes getting the basics right is more important than having an exact Vo2 measurement.

It’s not useful because it’s not really an indicator of one’s ability to perform and can’t really be affected through training. It’s primarily affected by genetics and weight.

That said, it does provide some correlation to an athletes performance “ceiling”, and you’ll typically find elite endurance athletes are naturally blessed with an impressive Vo2 max. You’re not going to win the Tour de France with a Vo2 max of 50 no matter how hard you train, just like you’ll never play Center in the NBA if you’re 6’1.