I thought the same when I first saw "stock" Rider - it's a very different look and feel from Visual Studio, more what you'd be used to as a Java dev with IntelliJ, or an Android dev with Android Studio. I personally found th look a bit... dated.
A while back JetBrains made Rider more themable (prior to that update, you could only really theme the editor, not the file explorer etc). After that update, it looks great with a dark theme enabled!
I'm on mobile now, but if I remember later I'll mention the name of the theme I'm using - it's pretty close to VS's dark theme.
That's one of the out-of-the-box themes, but I just checked and the theme I use is called "Visual Studio Code Dark Plus", and I use the colour scheme with the same name. You can find it as a plugin here:
https://plugins.jetbrains.com/plugin/12255-visual-studio-cod...
A while back JetBrains made Rider more themable (prior to that update, you could only really theme the editor, not the file explorer etc). After that update, it looks great with a dark theme enabled!
I'm on mobile now, but if I remember later I'll mention the name of the theme I'm using - it's pretty close to VS's dark theme.