There is no denying that good UX/UI is important for the success of any website or application. After all, users are more likely to stick around and use a product that is easy and enjoyable to use.
However, it is important to keep in mind that UX/UI is just one part of the equation. A website or application can have the best UX/UI in the world, but if it doesn't offer something of value to users, it is not going to be successful.
Think of it this way: A website or application with good UX/UI is like a car with a comfortable and stylish interior. It's great to have, but if the car doesn't have a powerful engine or good gas mileage, people are not going to want to drive it.
The same is true of a website or application. If it doesn't offer something that users want or need, they are not going to stick around, no matter how good the UX/UI is.
So, while good UX/UI is important, it is not the be-all and end-all of website or application success. The most successful websites and applications are those that offer a great user experience and offer something of value to users.