The NBA is such a different beast from college ball though. I did a quick look this morning, and pulled 601 players on NBA rosters currently, which includes draft picks but not summer league guys like Boo and Chase.
15% of the league's players (~90) didn't play college ball. A quarter of the players (~150) came from 10 schools - Kentucky, Duke, UCLA, Kansas, Baylor, Gonzaga, Arizona, Michigan, UNC and Villanova. Of the remaining ~360 players, half come from 26 schools that have 5+ players, and the rest come from 95 different schools.
The median years of experience in the league is 3. For players that have been in the league 3 years or fewer, 19% (57) didn't play college ball, 26% (78) come from 10 schools - Kentucky, Baylor, Duke, Arkansas, UConn, Gonzaga, Houston, Kansas, UCLA and Virginia. The other 170 are spread across 92 schools, of which 127 come from 60 P6 schools. So that's an average of 0.46 NBA players per team per season, many of whom will likely not even make the opening day roster.
I guess what I'm trying to say is that there are plenty of teams that make the NCAA tourney each year without NBA-level players