...still single
Repeat this to yourself 10 times :
1 - "most pilots on pprune think VASIS is better"
2- "PAPI is cheaper than VASIS"
I am happy to repeat your statement :
"If ICAO says it's good, then it must be good". Sure PAPI might be "good enough" for ICAO but still not be better than VASIS (as most pilots agree). PAPI is also cheaper to install, so this might be part of the reason ICAO choose PAPI.
PAPI might be more "cost effective", but not the best means.