For me, I just believe there are better players available in the top 4. I wouldn't hate if we picked Drysdale, because he would immediately become our top prospect, but no matter how the top three shakes out, there will be at least one or two forwards I like more at 4th overall.
There's talk about every player outside of Lafreniere potentially being available at 4th overall. It's unlikely that Byfield drops, but he would be my first choice. Same goes for Stutzel, being my second choice. If that's the top 3 though, I'd still be leaning Raymond at 4. If it's none of those players, I'd have equal amount of intrigue / excitement / concern with Perfetti, Rossi, Holtz, Drysdale (in no particular order). Anyone outside of those guys, I'd have varying levels of disappointment...
Definitely things to consider, but neither should be a determining factor. Always take best player available, regardless of "need".
If Yzerman believes Drysdale is the best player available, he should pick him. He shouldn't pass on him just because he feels we already have our top four right side in Hronek and Seider. Or just because next year's draft is loaded with high end defensemen.
I'd argue that our biggest need is a right-handed sniper to flank the left side of our power-play, opposite Mantha / Zadina. However, Yzerman shouldn't reach for a player like Holtz to fill that spot, unless he and his scouts believe he's the best player available at 4.