It's OK. It is slang for the loo though, especially in the USA. Also, Johnnie is slang for a condom. (old slang, maybe but still used a bit.) I suppose some other names could be mocked, but there are many that wouldn't be. Up to you though if you want to call him that. You can't be sure about it of you're asking people on the internet what they think though.
I am liking these proper old century old names like Flo, Hilda, Arthur, and Nellie! (Haunting of Hill House and Under the Dome have a Nellie in, both 20 something young women.)
If I were to have a daughter now, I would call her Eleanor - and shorten it to Nell, and if it was a boy it would be Arthur, shortened to Art. Lovely, classy names.
(IMO.)
No to Garry and Kevin and Barry and the like! And no to Finn. Will lose its appeal quickly.
No idea why anyone would feel sorry for a GEORGE. (As @oatsbeansbarley said. Though I have never known one personally oddly! Alan is a lot worse a name for a young child IMO, even though @oats said that should make a comeback!
As a pp said, I don't know any boys, or young men called John. None under 40 actually. Don't know whether that makes it a good idea to call your son John, or a bad one.