@juanitofut6 , I agree that Vivaldi's default theme is something, ehm, let's say, crappy. But I think this is what encourages the user to configure it to the style they like, a practically infinite possibility in Vivaldi, not only from the configuration and themes available, but also with the CSS modifications created by the users that you find in this forum.
If you go through the 'Post your color sheme at Vivaldi' subforum you will see that there are so many possibilities that seem to be completely different products and they are not all from the same browser.