Far below average plagiarizing law student Joe Biden was never qualified to say anything about constitutional issues. Any attorney general, solicitor general, white house counsel, etc. of the past decade could speak with at least slightly more credibility, or less senility, about that.
If it is popular enough to pass, then Congress or a national convention can propose it again and states can ratify it again. If that doesn't happen, then it still doesn't have the national consensus needed for a constitutional amendment.
Mostly I see this as a diversion. Somebody thought of something to tell Joe to take attention away from Trump.