It's not that Slavic beliefs are unpopular. Most of Slavic mythology was passed down through family generations in the form of stories, and very little was written down, so it is hard to find solid first hand Slavic writings.Then of course in the 7th century, Christianisation began to settle in and the stories grew even more scarce.
Despite this, there are still some tales about Slavic mythology around. I know that they too have a 'Tree of Life', which is similar to other paths. A few major deities are Rod, the creator god; and Perun who was seen as the 'main' god and presided over thunder and lightning, similar to Zeus in Greek mythology.
Here's a site with a list of many more Slavic deities, legendary mortals, mythological demons, etc., when you click on one it takes you to some background (including myths) on that deity: