Is there a plugin for this?

[NightWorldSky]

I want a SkyWars plugin where once you join one of the servers, you'd automatically join the game.

 

[NotSoBoop]

You could get the regular skywars plugin and put the portal underneath your spawn point, so when you spawn in you spawn over it and fall in.

 

[JustRayz]

You could get the regular skywars plugin and put the portal underneath your spawn point, so when you spawn in you spawn over it and fall in.

or get a plugin to run a command on player join to join them into a waiting lobby, and put in gamemode spectator

 

[NotSoBoop]

or get a plugin to run a command on player join to join them into a waiting lobby, and put in gamemode spectator

True.