Alabama had an incredible run of very good quarterbacks; Hurts, Tagovailoa, Jones, and Young one after the other. Milroe was taken after a preferred recruit switched and committed elsewhere. Milroe turned out to be a huge drop off from the previous string of quarterbacks; he is a fast runner but that's about it. He has limited Alabama's offense for two years now.
Simpson has a quick release and very good arm. I don't know if he is missing something that has kept him out of games or if there was something else going on behind the scenes. I believe there was something else going on as was kind of mentioned at the end of the video but it is only rumor as far as I know.
The freshman commit, Russell, appears to be very talented but at his current size, 6-3 180, he may not be physically ready by the start of the upcoming season. Russell would have to learn the offense and get moving on his strength and conditioning program. He is an early enrollee player so that will help.
I haven't seen enough of the current 3rd string quarterback, Mack, to know what to expect. The guy is huge though.