The average Wonderlic score is 20. This is a fair assessment test of intelligence. It is not fully comprehensive, of course, but decent enough.
Everyone knows McInally had the only perfect score of 50.
The average QB score is 26.
Fitzpatrick scored a 48. He was a Harvard graduate, so a good idea of what should be accepted as highly intelligent.
Wentz, and Alex Smith scored a 40, Eli a 39, Kaepernick a 38, Luck a 37. These are generally seen as very intelligent QBs.
Ryan scored a 32, Rivers a 31, Elway a 29, Cutler a 26. These are generally seen as above average intelligent QBs.
Favre scored a 22, Newton a 21, Carr a 20, Vick a 20. These are seen as marginally intelligent.
Feely a 19, Testaverde a 17, Bradshaw a 16, Shuler a 16, Young a 15, Mcnair a 15.
These are seen as below average in intelligence.
Jeff George a 10, Vince Evans an 8, Pryor a 7.
These are seen as far below average in intelligence.
With all of those as a reference point, Lamar Jackson scored a 13. With the Wonderlic as a decently reliable guide, Jackson is far, far below what is considered, even average, intelligent for a QB.
Of course, this is not a total guide for determining the ability of an NFL player or, even, a QB.
There are many black players that score high on the Wonderlic, including QBs.
For example, Calvin Johnson scored a 41, Demaryius Thomas a 34, Ben Watson a 48, Elliot a 32, Bruce Eugene a 41, Akili Smith a 37, Jonathan Ogden a 35.
So, many examples of intelligent black NFL players.
So, of course you can have an idea that Lamar Jackson is not intelligent. You can listen to some of his interviews and see his Wonderlic score. You can judge his intelligence, to certain extent, the same way you judge most regular folks. How they talk and present themselves. The way he did in college classes and what his degree was or was not in, etc.
That is not to take away from his athletic talent a all. He is very talented. Where his lack of intelligence might come into play is learning to read defenses and fix mistakes and take the hitch out of his throwin motions, etc. Teams will baffle lesser intelligent players.
You see this with players that rely mostly on mobility. As they age they have to become more adept at reading defenses, etc. For example, Cunnigham was an example of this. To an extent McNair and even Vick made adjustments.