"Let’s take this offline"

Without a clear, quick mention of how and when this “offline” conversation will take place, this is a jargony way to dismiss someone’s idea and put them off indefinitely.

And since any meaningful follow-up will likely take place online, it also no longer makes sense. Why not go with something like this: “That’s an important topic that’s beyond the scope of this meeting. I’ll email you when we wrap up.”