I'm not sure how they can say the early returns aren't great. Gay is scoring the most points per game of his career on the fewest shots per game (excluding his freshman season with more limited minutes). He's shooting .508, the first time in his career he has been over .500 (and he has rarely come close), and his TS% is also the highest of his career. He's getting to the line a bit more than he ever did and shooting well above his career average there. All of his other numbers are pretty much in line with his career, though his defensive rebounding, 3PT%, and TOs are a bit worse. Still, he has only been with the team for 1/3 of the season, and he's already #3 on total win shares on the team.
What is this "not great"? I don't get it.
That said, I wouldn't draft Smart at #1 in this draft, and I haven't seen Exum so I can't comment. But having seen Parker, having seen Embiid, having seen Randle (not the best fit next to Cousins, but still), and knowing the book on Wiggins (haven't really seen much out of him so far) - those guys are the guys you look at with the #1 overall. Smart is a tier down in my book, and I wouldn't be surprised to put Exum in the next tier as well had I seen him. At #5, Smart and Exum are in play. But not at #1.