Every designer knows the feeling. You can see exactly how something should look and feel in your head, then you build it, and what ends up on the screen is a flatter, stiffer version of what you imagined.
Ira Glass described this years ago, talking about creative work in general. You get into the work because you have taste, and for a long time your work isn't as good as your taste knows it should be. In his words, "your taste is why your work disappoints you." It shows up in writing, film and music, and product design is no exception. Some people quit because of it.
In product design, the gap is loudest in execution. A static screen can come close to what you had in mind. The moment it needs to move, respond and hold up under real interaction, the distance grows. That's where the experience actually lives, and it's where most designers' tools run out.
For a long time, the options weren't great. You could spend months learning tools built with engineers in mind, or settle for prototypes that hinted at the idea without delivering it. Either way, much of what you imagined stayed in your head or got lost somewhere between your file and the build.
AI is starting to change that. Instead of simulating an interaction, you can describe it and prototype it in working code. What you build behaves the way it would in the real product, not just the way it looks. The technical barrier that kept execution out of reach for most designers is dropping fast, and for the first time one designer can build close to what they see.
That's the part of the gap AI bridges, but Glass's gap has two sides. One is your hands not keeping up with your taste. The other is your taste itself, which keeps moving. AI can help with the first. It does nothing for the second, and I don't think it should.
Glass framed the gap as a phase you fight through until your work catches up. I don't think it ever fully closes. Every time your execution improves, your standards rise with it, and you start noticing things you couldn't see before. If AI removes the friction of building, what's left is a gap that's purely about taste. That's harder to face, because there's no tool left to blame. The only way through that part is the same as it's always been: keep making things, and keep looking closely at work that's better than yours.
That's also why the gap is worth having. It means you can still see further than you can reach. If you're feeling it, you're not behind. You're growing, and the gap is growing with you.