Well, when you look at the trio we discover something new about each one of them in the story. Rey is a Palpatine, Poe was a spice runner, and Finn is Force-sensitive. I’d hate to deny him something new. But at the same time, if I did do the inspirational message thingy for him that might work as a substitute.
Honestly, I feel like they just didn’t know exactly what to do with his character in TROS. I can kinda see what you mean when you say that if he’s Force sensitive it kinda diminishes the idea that anyone could defect from the First Order. Which is why Jannah and Co. was introduced, and why I’ll likely have other First Order troopers help them against the Final Order.