When Taekwondo was developed, it was based upon centuries old empty hand self-defense fighting techniques. Humans have not evolved significantly in the last few hundred years, so these fighting techniques are still pertinent today. Traditional Taekwondo, while used in competition, is still effective for empty hand self-defense against untrained attackers. Sport Taekwondo is for competition free-sparring mostly; it effectiveness for empty hand self-defense against untrained attackers is questionable. Neither version is great in fight (as explained later) but some of their basic techniques are applicable, but then Taekwondo practitioners should not be entering into fights.
Since humans have not evolved significantly, their methods of empty hand combat have not changed significantly, they have only been refined through scientific research. Personal weapons, other than firearms, have also not changed significantly over the centuries. Certain personal weapons, such as swords, mace, and Tasers come into and out of vogue, and certain weapons, such as knives, have been refined but they are still service the same purpose s they did ages ago.
Personal weapons are used to strike, cut, or puncture (such as by stabbing, spearing, or being shot with a projectile). Most traditional martial arts weapons are no longer used; however, some are still in vogue, such as knives and burgeons. Since traditional weapons, such as knives, have not changed much, traditional self-defense methods against them are still effective. Personal weapons of the future will primarily involve electronics, such as weapons that temporarily stun, blind, or disorientate an attacker.
One point to remember is that most traditional Taekwondo self-defense methods assume the attacker is not a trained fighter, so the techniques learned and practiced in patterns and step-sparring are best used against untrained attackers and are practically useless in free-sparring. When the attacker is a trained fighter, traditional defense methods or modern free-sparring techniques may not be effective, especially since the attacker will know what techniques you will probably use and, since fights usually involve anger, training usually does not enter the mind. With the proliferation of martial arts in the last few decades, it may be assumed that your attacker will have had some martial arts training at some point, either in the military or as a child in martial art schools.