NBA allows these guys to enter the draft one year removed from high school. Look at the readiness to compete and be strong contributors of NFL vs NBA rookies. Percentage wise. To come out early, you have to sell yourself as one of the top 60 players in the college ranks (or non-NBA world ranks). I'll list the 10 draft picks from the 2016 NBA draft. Anyone heard of these guys after leaving college? Honestly, did you hear their name through the NBA season, other than about Simmons being hurt and maybe Buddy Hield (played 4 years of college ball) some for good play. I'll list there production below also. These guys come in for the easy quick money and are usually not ready for the level of competition and talent they are facing. Their game is just nor refined enough and mature enough. Wonder why... Heck, there's been a good number that leave early that don't get drafted, again as there are only 60 picks. It's just my view, but I don't like the rule. Of note, only 2 of the top 10 picks played more than 1 year of college ball (Hield and Dunn).
#1 Pick - Simmmons, did not play due to injury
#2 Pick - Brandon Ingram, avg. 9 pts, 4 rbs, 2 assts
#3 Pick - Jaylen Brown, avg. 6.6 pts, 2.8 rbs, .8 assts
#4 Pick - Dragan Bender, avg. 3 pts, 2 rbs, .5 assts
#5 Pick - Kris Dunn, avg. 4 pts, 2 rbs, 2 assts
#6 Pick - Buddy Hield, avg. 15 pts, 4 rbs, 2 assts
#7 Pick - Jamal Murray, avg. 10 pts, 2.5 rbs, 2 assts
#8 Pick - Marquese Chriss, avg, 9 pts, 4 rbs, 1 assts
#9 Pick - Jakob Poelti, Avg. 3 pts, 3 rbs, 0 assts
#10 Pick - Thon Maker - avg. 4 pts, 2 rbs, .5 assts
So these top 10 picks averaged 6.3 points per game, 2.2 rebounds, and 1 assist per game. I can't find good recent stats to determine the average of these three stats for a starter on an NBA team, but I'll bet you big money, it's well above 6 points, 2 rebounds, and 1 assist per game. None of these guys were anywhere near all star talent. Look at the first round of the NFL draft from last year. There's more guys in that round that ended up starting for their teams than those who didn't. The first 18 guys are all solid starters for their team, with the #1 pick Goff, having the toughest year. Not even comparable which league brings in more ready talent.
Now, will someone push me off this soapbox, I'm getting old...