Zone of Truth 5e | D&D 5th Edition

You can generate a magical zone that Deception in  a 15 Foot radius Sphere against the guards centred on a point of your selection with in the rage. Until finish the spell, a Creature enter the spell’s field for the first time on a turn. Creature start its turn  and must make a Charisma saving throw. A Creature can not speak a lie on a failed save while in the radius. You know the already whether every creature can succeeds or not on its saving throw mode.

What is the point of Zone of truth?

A Creature who has affected is aware about of the spell and thus avoid of answering the question for which it would simply responded with a lie. This type of creatures can be evasive when its answering as long as it can remain within the area of the truth.

Is Zone of truth  practically worthless?

So the people who enter the spell’s area know very well that they have entered and can simply plead the 5e or they can give random answers to any type of question. It’s a logic behind of this, someone who get hit by it, they can save the fail, now they are unable to lie, if you do it “yes” or “NO” If you unable to speak answer you will defeat. Then they have opportunity, honesty or death, If they select for NO Answer, they  found guilty and get die.