I came across Create Thrall when I was making my character for Curse of Strahd. I decided to go with Goolock for thematic reasons, and made a list of every way to incapacitate someone in 5e, even knowing the campaign doesn't get to level 14. Hypnotic Gaze still stands out to me as the clear winner for being recyclable and also a really strong ability on its own, as well as not (RAW) breaking Sanctuary.
I still think Goolock is weak (this can't affect non-humanoids, which I find a little disappointing), but nowhere near as weak as before. Honestly, this could make a GREAT villain.
This is true, although ways to do this in combat are limited. The torpor poison is the only non-magical way to do this if you don't count unconscious as being asleep (which, technically, is a better description), although all 3 other poisons inflict this condition, as well as Eyebite.
It's true you can just wait for the target to be asleep, but the point is that you can do this mid-combat over 2 turns and there really isn't much anyone can do about it.
They could switch to support. They can't hurt you, but that doesn't stop them from buffing their allies. By RAW, they can also use area effect spells and hurt you without targetting or attacking you. And they could do help actions to give allies advantage when attacking you.
Again, true. That's part of why I selected Hypnotic Gaze as the ability that's an ideal combo, since you can also incapacitate them indefinitely, provided you forego an action each turn. Can't do any support or AOE if they can't act.
But then it's not a combo. You're just using Hypnotic Gaze. No point in Charming them if you're keeping them incapacitated.