I don't think anyone is arguing if it would be technically possible - engineering solutions exist for almost anything these days - it's just that it wouldn't be a financially reasonable project.
A fun fact is that Ohio DOT did have preliminary plans for a cross-lake interstate to connect Cleveland to London back in the 1970's, as it's a much shallower lake and could be done with a Lake Pontchartrain causeway type project. It obviously didn't go anywhere at the time.
I'm surprised they went with a causeway idea rather than a tunnel. I would assume ice / ice flows in the winter would make this annoying, plus you need a higher section somewhere for ships to cross unlike Lake Pontchartrain. I guess you could also do tunnel/bridge hybrid but that adds complexity.
This connection would be a fun nice-to-have, but nothing more.