Disagree. There’s something about the “able” that implies a hindered routine ability to do something — you can otherwise do this, but something renders you unable.

“I won’t be able to make the 5:00 dinner.” -> You could normally come, but there’s another obligation. There’s an implication that if the circumstances were different, you might be able to come.

“I cannot make the 5:00 dinner.” -> You could not normally come. There’s a rigid reason for the circumstance, and there is no negotiating it.