Yeah, that sounds like it is so much more competitive than the ACB. 
In fact, D1 NCAA basketball is fairly competitive, nationally televised, and has a ton of money involved in it. The fact that those players aren't formally compensated for their services doesn't mean as much as people think it does.
Yeah, that's why we still send nothing but NCAA "amateur" players to the Olympics to compete with those international players. No need at all to use more seasoned, professional NBA players to dispatch those inferior foreigners... Oh wait ...
You got the
bold part right, at least.
Seriously, your view sounds about right ... up until the early 1980s.
Internationally-sourced players are a bigger and bigger part of the NBA. Last year, a record 1 in 5 NBA players on opening day rosters were sourced from international territories. Only a tiny handful (2 or 3) teams in the NBA did NOT have an international player. The Spurs, of all teams, lead the way with the most such players on their roster.
Contrary to the apparent opinion of several on this blog, the "bust" rate of international players who have been drafted in recent years is not really much different from that of NCAA-sourced players. For lottery picks, the bust rate is about 1 in 3. That increases as you go deeper into the draft for both NCAA and Internationals.
Again, none of this means that Kristaps is necessarily worth taking at #17. But your blanket dismissal of international competition as somehow being vastly inferior to the NCAA has no foundation. There is no real basis for that assertion. Last I checked, we haven't had a lot of competition going on between Spanish ACB teams and NCAA Division 1 teams. College-only US teams that compete in international competitions no longer dominate outright like they did decades ago. Obviously, some international leagues are stronger than others. Just as some college hoop programs are stronger than others.
It is perfectly reasonable to be more confident in assigning draft value to players that you know more about. Uncertainty is risk and that is negative value. So to say you know more about domestic players and thus are more comfortable ranking them higher is perfectly fair.
One hopes that if an NBA GM does decide to scout an international player, though, that he will put in just as much due diligence into that selection as he would for an NCAA player and not foolishly dismiss them due to out-of-date prejudices.