Ah, the loner. The lone ranger, the self-appointed outcast, the dark and brooding mysterious scavenger-warrior who wanders and waits for their time to come and more oft than not, refuses assistance except perhaps from one trusted friend. Such figures fill literature and film, and we recognize them immediately. Aragorn, Gandalf, Han Solo, Yoda, Halt, Batman, James Bond, Rey, Captain Jack Sparrow, the list could go on. Antagonists frequently fit into this category as well. Protagonist or antagonist, the point is, this character archetype frequents writing. While I used to find such a character appealing to read and to write, I'm now a little more cautious to use them in my work and in recommending using them to other writers. Why? In this social day and age, I would say the loner who chooses to be a loner is no longer a romantic ideal that readers, especially teen readers, find appealing.
I think we need more characters like Thomas, who strive for interactive relationships with those around them, than loners in fiction, especially YA. We live in a social world where we interact constantly. Characters who find that unattractive and would rather live in an empty world without friends (except one or two friends they choose, which basically makes them social jerks [#sorrynotsorry]) are not as relatable. I know this for a fact because in my own work, The Red and the Scarlet, all of my betas found my main character Fyr, who starts out as one of these Loners, unrelatable and annoying, even, and gravitated toward my more social supporting characters. But as the story progresses and Fyr starts to reach out to those around her in an attempt to befriend people out of empathy as opposed to self-interest, my betas started rooting hard for her. For teens especially, the character reaching for friendship (whether successfully or unsuccessfully) as opposed to choosing to shut themselves out is more relatable.