Pidgin by itself won't really do anything. It's the software that you use to connect to a chat server, and that's where your contacts would be stored. So anyway, if you just install Pidgin and stop there, no one will be able to locate you, because you won't be signed into anything where other people are also signed in.
You might be able to still use Pidgin to sign into some old networks. AIM is gone now so not that one. Like you said Google Talk has moved to Hangouts (GTalk used to be XMPP). I'm not sure if you can still use Pidgin to connect with GTalk/Hangouts in some way at all -- for a long time there was a deprecated but still-working way to do that (last verified years ago, no idea of current status).
You could look into XMPP. Pidgin connects to XMPP servers just fine. There are numerous servers around the world; you can run your own or join one that someone else runs. A cool thing about XMPP is that you can chat with and have contacts with people on OTHER XMPP servers, kind of like email but real-time. You can have private conversations or join group chat rooms. For tracking down people you already know and chatting with them over XMPP, I'm not sure how you'd do that other than connecting with them first some other way and exchanging addresses ().
Good luck!