Tristana Rocket Jump

Because Tristana's doesn't make her untargetable.

Anything that looks like a jump are just visuals (such as Trist's W or Kha's E), but the coding is coded as a Dash, so technically, you'll still be pulled/hooked/snared.

Fizz's E makes him untargetable, which is a totally different case than Trist's or Kha's jump.

Fizz is balanced around being untargetable. It's unique to his kit. Trist is balanced around being targetable...

Because Fizz's E is made for him to be untargetable. It's called Playful/Trickster for a reason. Besides, it's his only Engage/Escape tool, while Tristana has her other abilities. Meanwhile, Tristana's W is just a single-part Dash that can scale walls. I Main her and love her kit, and I don't see any reason why she should be untargetable while Rocket Jumping. Her Dash even goes much farther than Fizz's, and just increases with Level thanks to her Passive. What it looks like is you had a bad game against Blitzcrank. Don't let it get to you, it happens to all of us. Make sure to understand how Blitzcrank works, and adapt your playstyles to combat or get around it; it's the only way you'll get better in League.

Her jump is coded as a dash, not an actual jump