I've never broken down tape of Schultz, I've only seen brief clips of him mostly on Zeke runs, but from what I've seen in those his blocking has flat out sucked. Like he didn't even know which man to block half the time.
The learning curve of Y tight ends is long, because they have to learn an NFL blocking scheme and an NFL receiving tree and execute both against the best athletes they've ever faced. That being said, Stanford is one of the last few schools to use an in-line TE, so we've usually seen Cardinal TEs come into the league more prepared then what Schultz was. Hooper, Ertz, Fleener - as far as I know, they were all day 1 starters while Schultz was inactive behind Rico for half the year. And once I saw some of the blocks he was whiffing, I kinda understood why.
He's in a bad spot IMO. A guy who both needs to develop more strength to block and learn the blocking scheme better, and who offers little promise as a receiver. He's a pretty smooth mover for his size, but he's not big enough to box out LBs for a catch nor explosive or fast enough to separate from them. College LBs were hanging with him pretty easy, and again, I haven't watched him, but I'm guessing he's an easy cover for NFL LBs too. Dude needs a lot of development, in a lot of areas, fast.
I know it seems like I'm pounding a whole bottle of Haterade here, and I'm usually a glass half full kind of guy with rookies, but I just am not seeing much with Schulz. At the minimum, he's got to pick up the blocking scheme by the beginning of year 2 and learn to put his hat on the right man. If he doesn't - I'm calling it now, there is a real chance he doesn't make the 53. He deserves another shot due to that long TE development time, but this staff really values blocking in TEs and they're not going to keep him around for long if he can't do that.