Yes, it feels that way doesn't it?
The only remaining service I now use with pidgin is gtalk, but it doesn't support offline messages. Or rather, Google didn't implement them in XMPP, so as a result there is a black hole where sent messages go into and I never see them unless I log into Google's Hangouts with a browser.
Yahoo actually stopped being supported in Pidgin last year I believe; due to some major breaking changes in the protocol.
I know what you mean though, it was weird when AIM shuttered, my account was old enough to vote. It is a strange thing when something that was so integral to your life at one point no longer exists.
It was more painful when bbses died but we were all hopeful. Not the same today.
You say you have an air-gapped PC that supports XMPP and ICQ?
Sorry, mixing my pronouns. Pidgin as downloaded from the internet today still supports those protocols.
My air-gapped PC supports the Windows XP tour and erm Hover! and that's about it.
It supports XMPP and ICQ protocols still, but my goodness, I'm now learning what it means to be old and lose the systems I used during my formative years. Is this what it felt like to have BBSes die? Yes they still technically exist, but their 'mainstream' days are behind them.