How vital is user interface design in remaining engaged with an application ?

I’ve been thinking about this lately after trying to improve my daily routine with a few different self-help apps. At first, I was really motivated, but after a week or so I noticed I kept dropping them one by one. The weird thing is, the features were actually useful, but something about the interface just didn’t feel right — too cluttered, too many buttons, or just not visually ????????. It made me wonder if UI design plays a bigger role than we think when it comes to staying consistent. Like, even if the content is great, can a ?????? ????????? completely ruin the experience? Curious if anyone else noticed that.