Obviously, you can customize the look of any distro yourself, and use themes and icons and such to make it look better.
But here, I'm talking about distros that look beautiful without any tweaking or customization work from the user. These distros offer a friendly, smooth, and out-of-the-box desktop experience.
1. Deepin Linux
Deepin Linux is a nice Linux distribution that originated as a stable branch of Debian. For some, its animation may be a bit excessive, although it looks beautiful. It has its own signature Deepin Desktop Environment, which is packed with basic features to provide the best possible user experience. It may not have the same user interface as other distros, but you can easily get used to it.
2. Pop!_OS
Pop!_OS, while providing a pristine GNOME experience, has also managed to build an excellent user interface on top of Ubuntu. This is my favorite and I use it as my main desktop system.Pop!_OS is neither flashy nor has some fancy animations. However, it does the best it can with the perfect combination of icons and themes, while enhancing the user experience from a technical perspective. I don't want to start a debate between Ubuntu and Pop!_OS, but if you're used to Ubuntu, Pop!_OS might be a great choice for a potentially better user experience.
3. Manjaro Linux
Manjaro Linux is an Arch-based Linux distribution. While installing Arch Linux is a slightly more complex task, Manjaro provides a more comfortable and smooth Arch experience. It offers a variety of desktop environment versions to choose from at the time of download. No matter which one you choose, you still have enough options to customize the look and feel or layout.
4. elementary OS
It offers Linux users an excellent experience thanks to a macOS-like look. If you are already acclimated to macOS, then you won't feel any discomfort when using elementary OS. Moreover, the elementary OS is based on Ubuntu, so you can easily find a large number of applications that can meet your needs. More than just the look and feel, Elementary OS always strives to introduce some important changes. Therefore, you can expect the user experience to improve with each update.
5. Zorin OS
There is no doubt that Zorin OS is an impressive Linux distribution that strives to provide a good user experience, even with its streamlined version. You can try the full version or the lite version (using the Xfce desktop). This user interface is specifically customized for users who are used to Windows and macOS. Although it is based on Ubuntu, it still provides an excellent user experience.
Feel free to disagree (politely, of course) and suggest your favorite Linux distribution.