Depends on the rim and the rider; on a Zipp 808, it would be fine for pretty much anybody, on Mavic CX18s it would be OK for a skinny pursuiter but for a big sprinter not so much. Bear in mind that loads of road wheels are 16/20, and road sprinters don't seem to be troubled by them. Old fashioned spoke counts had more to do with a combination of very light (and therefore noodley) rims and poor fatigue strength of spokes. Both have changed a lot in the modern era.
Depends on the rim and the rider; on a Zipp 808, it would be fine for pretty much anybody, on Mavic CX18s it would be OK for a skinny pursuiter but for a big sprinter not so much. Bear in mind that loads of road wheels are 16/20, and road sprinters don't seem to be troubled by them. Old fashioned spoke counts had more to do with a combination of very light (and therefore noodley) rims and poor fatigue strength of spokes. Both have changed a lot in the modern era.