Why can't I play multiplayer in Minecraft Java?

I can't play the multiplayer in Minecraft Java

You have to click on "add server" or on "direct connection" and then enter the server IP of the server you want to visit.

But you can, you just have to choose the server and enter the ip address under 'direct connection' and that's it…

I can't play the multiplayer in Minecraft Java

and what gives you the impression that you can't?

There's just no server on your local network, so you'll have to add an external one