I usually copy paste screenshot of the result as a feedback, and use a couple of round of reviews after the first iteration. I also use it as a though partner on itself, asking it to take the role of a master ux designer, or expert sales person to find design flaws, and suggest improving the result... I am ditching intellij and Juno. I don't really like the editor on itself, because I am used to have my intellih shortcuts, but Gemini produces wonderfull code for me. Maybe because I give it good prompt. And the project I am building is a public good for society and the environment, so maybe gemini likes me more than he likes you... Who knows!
I suspect their core issue is (1) low quality instructions and system prompts (2) lost all their good PMs & designers