I worked on modding Quake 4 and Doom 3 a long time ago. I have worked in the Unity engine. I know C++, C#, java--that family. I have done game engine programming (15 years ago), gameplay programming, AI, tools, etc…. all 10 years etc. ago

What are the current technologies that are things I should know if I want to compete/participate after being derelict for so long?