It's normal that systems get changed and improved in an on-going development. That doesn't mean content was "removed" in my eyes. The skilltree might look different than in the past, but as far as I remember it only added new skills rather than reducing the options.
A huge amount of content was added since 2022. If you haven't played since then, either go around and explore all the changes by yourself, or you can check out the "Change log,txt" file in the game folder to see everything that has been changed since you last played.