^Rey finding self worth for herself alone, would still serve Rey better than the ol’ friends-and-family-help-me-realize-what-it is-vaguely. You’re Not Alone and being validated by everyone, is not the same as accepting Being Alone and trying to make something out of it. The fact that she even has something tangible to reject to find purpose already takes a lot away from her TLJ arc.
If you’re referring to the scene with the Jedi of the past, they’re not giving Rey validation. They’re encouraging her to stand against Palpatine, regardless of how weak she is in comparison to him. They’re giving her motivation.
“You’re not alone” refers to one of the symptoms of her core belief of self-worthlessness, that being feelings of loneliness. And she turned to the Jedi of the past for help because she felt alone and unable to stand up to Palpatine after he sucked up her life force and threw Ben into the pit.
There’s really no justifying this imo - Rey Palpatine is a completely different arc, and if you think otherwise I don’t know if you understood the ethos of TLJ.
How is it a different arc from her self-worth arc? And I already explained in the post as to why it doesn’t undermine her TLJ arc as well as why said arc is misunderstood by even the most loyal TLJ fans who dislike TRoS.