BfA and Shadowlands both hurt a lot of Forsaken interest indeed but we are far from gone. There are plenty of RPers and guilds about. We are just not as abundant as the popular races. A quick scroll on the forums here reveals various undead guilds.
You can also find a collection of us over at the UndercityUnited discord server.
https://us.forums.blizzard.com/en/wow/t/undercity-united-20-weve-moved-to-a-new-server/1280393