No, you didn't understand me correctly. Of course that as long as Ivy has both the Trait and the Drill, it is extremely hard to get out of her Zoning, but while she has no access to her Trait, it is very easy to jump off the ground and avoid the Drill. That's what I meant. Shinnok's Hell Sparks in MKX also come from the ground, but their range is much bigger, that's not the case with Ivy's Drill.
On top of that, once the trait is on cool down (which is not that fast, mind you), Ivy must go back to her Rushdown game even if the Ivy player doesn't want to. She needs both the Trait and the Drill to Zone effectively, and if one of those tools (the Trait) is a time based tool and Ivy can't have access to it at every given moment and she has to change her game not because of the opponent's decisions but rather Ivy's own tool set, that's not that much of an effective Zoning. Other characters can Zone much better not just because they have more then one Zoning tool, but also because they have access to all of those tools at every given moment. When I'm playing Reptile in MK9 and MKX and I wanna go for Zoning, I don't need to wait for any of my Zoning tools to have it's cool down getting over because they don't have any of such. What would happen if you go to an MU in which you have to Zone and the Trait runs out? You stuck in a playstyle that you don't want to use even if it's not gonna help you. That's the thing about Ivy's Zoning.
Also for the record, yes projectiles are the only tools that can Zone, back to Shinnok in the Necromancer Variation, only the Hell Sparks are long range projectiles, he has that short range range projectile as well, plus the Necro specific moves that aren't projectiles yet can still Zone.
And yes the opponent can just use push block to get the Trait close pressure end and let it go for cool down, I just mentioned the fact that you can use the trait for Pressure in addition to Zoning just to show that if her time based Zoning tool can also be used for Pressure, in addition to her 100% accessible strings and mid-range tools, she is much more of a Pressure character, that just happen to Zone when she can.