The wording for "Create Thrall" in 5E seems a bit rushed and not very clear.  This ability is for the pact of the old ones warlock.

What is a Thrall?  It is someone who has been forced into service of someone but who doesn't dare try to escape.  However according to how this ability is written all you do is charm the person and create a telepathic link to their mind.  Charm in 5E only makes them a friendly acquaintance.  That is not a thrall.  So... how can we fix this?

Why does it need fixing? It's a powerful ability that can get NPCs to do your bidding without allowing a saving throw.

Class feature and spell names are often figurative. Mage Armor doesn't actually create armor. Colossus Slayer works on enemies of any size. Whirlwind Attack doesn't involve a whirlwind. Open Hand Technique and Lay on Hands don't require hands. The Daylight spell doesn't create sunlight.

It dosen't make anyone do your bidding.  It give you advantage on trying to persuade them to do things.

Yes, and then you can persuade them to do your bidding.

So, this is the Dungeon Masters Guild thread--perhaps you meant to post this in the Rules & Game Mechanics section?... thread was moved.

As to your topic, it appears that the intention was to give the Warlock an ability that allows them to charm an incapacitated humanoid for a nearly indefinite amount of time. To fix your problem, why not just change the name rather than try to create a new ability? Something along the lines of "Charmed Contact" or "Beguiling Touch," perhaps even "Enthrall" could work. 

Even then, I'm not convinced the wording is unclear. A quick Google definition of thrall is simply: "the state of being in someone's power, or of having great power over someone." Being able to force a person to think you're their friend, regardless of their true feelings toward you, fits that definition. I'd say it's important to note that the word thrall does not mean complete and utter obedience.    

You don't force them to be your friend.  Charm in 5E makes them a friendly acquaintance.  Back in 3.5 It made them your friend.  If it did that then it would be a thrall.

For a different ability then, here's three creatures that can completely dominate a creature's mind and body: the intellect devourer, ghost, and cambion. I used abilities from those monsters to create something that fits your paradigm a little closer... 

Intellect Devourer's body thief feature

Create Thrall. The warlock initiates an intelligence contest with an incapacitated humanoid within 5 feet of her. If she wins the contest, the warlock magically takes control of the target’s body. The warlock knows everything the creature knew, including spells and languages.

If the thrall drops to 0 hit points, the warlock must sever her link to it. A protection from evil and good spell cast on the body also completely severs the link. By using an action, the warlock can voluntarily sever her connection to the thrall. The thrall's body then dies.

Ghost's possession feature

Create Thrall. One humanoid that the warlock can see within 5 feet of him must succeed on a DC 13 Charisma saving throw or become a thrall; the target is incapacitated and loses control of its body. The warlock now controls the body but doesn't deprive the target of awareness. 

The thrall lasts until the body drops to 0 hit points, the warlock ends it as a bonus action, or warlock is turned or forced out by an effect such as the dispel evil and good spell. The target is immune to being turned into a thrall for 24 hours after succeeding on the saving throw or after the ability ends.

Cambion's fiendish charm feature: 

Create Thrall. One humanoid the warlock can see within 30 feet of it must succeed on a DC 14 Wisdom saving throw or be magically charmed for 1 day. The charmed target must obey the warlock's spoken commands. If the target suffers any harm from the warlock or from another creature or receives a suicidal command from the warlock, the target can repeat the saving throw, ending the effect on itself on a success. If a target’s saving throw is successful, or if the effect ends for it, the creature is immune to the warlock's create thrall ability for the next 24 hours.

keep in mind that Charmed is very broad now.

All of the Dominate Spells, use the mechanic "Charmed".
I personally see the Thrall spell as a more permanent Dominate.

5e struggles with this, it feels like parts of it were written, then other parts that dramatically change the meaning. Charm spells are incredibly weak now. The charmed status, is very very weak compared to what it was before. The INTENTION here, clearly reads like they meant to make this like dominate, or a vampire's charm, but RAW, this is almost worthless. Your "Thrall" can cheerfully try to murder everyone in your party, except you, and you have advantage on persuasion, but since you can't use persuade in combat to make someone do what you want them to, Rules as Written, this is toothless. I wish they would clarify it in Sage Advice.

Why can't you persuade someone in combat? Sure it wold take your whole turn but with advantage you could probably convince them to stop attacking your friends

Now I am picturing familiars from What We Do in the Shadows. Gizmo, I mean Guillermo, is Nandor's thrall... he does his job but isn't exactly enslaved. Of course Nandor doesn't use telepathy to communicate with Guillermo, he uses regular yelling.

Looking at this in 2025 and they changed Create Thrall to have nothing to do with thralls at all. Now it lets you cast summon aberration without using concentration and gives the aberration some extra abilities. Not a bad ability, but the name makes even less sense.