I think if you want to rule it that way the RAW allow that interpretation. I don't really think it's the intent of the rules, though, since this edition - like the last few previous editions - generally seem to be on the "yes with a penalty" side of the fence with rulings rather than a "no you can't do that" side. So it doesn't "feel" right to me to disallow it entirely even though it could be argued that you could read the rules that way. And on the other hand, the idea that you're going to fire a longbow point blank into someone you're engaged in melee with doesn't "feel" right either - so I can see how you'd want to disallow it.
Though if you had an ally engaged with the same target who could distract them, then we get back to where I think it would be okay to shoot them point blank with a longbow - so really the problem for me is less about the distance and more about whether or not they should be able to interfere with your shot, which brings it right back to disadvantage sounding like the right thing to do. (To be honest my ranged player wouldn't even think to try to fire with disadvantage rather than switch to a melee weapon, so it's literally never come up).
Though if you had an ally engaged with the same target who could distract them, then we get back to where I think it would be okay to shoot them point blank with a longbow - so really the problem for me is less about the distance and more about whether or not they should be able to interfere with your shot, which brings it right back to disadvantage sounding like the right thing to do. (To be honest my ranged player wouldn't even think to try to fire with disadvantage rather than switch to a melee weapon, so it's literally never come up).