IQ is a reasonably effective metric of certain kinds of intelligence. It doesn’t measure all intelligence and has some caveats, but it still highly correlates with certain abilities of one’s brain. IQ decreasing over time in the same subject is a cause for alarm.

And you absolutely can objectively measure certain types of beauty. If you managed to rank all of humanity by facial symmetry, I’d think you were a bit weird, but I wouldn’t say that you were wrong.