I think the reason why Kylo is so hard to sympathize with his because the character Finn exists.
Kylo was born with wealth, privilege, a loving family, and Force powers. Finn was an enslaved child soldier with no family and nobody who cared about him.
Kylo may have been influenced by Snoke but he was also influenced by Luke, Leia, Han, and Jedi values. Finn grew up hearing nothing but First Order propaganda.
Yet when the time came for them to make a choice Finn made the right one and Kylo made the wrong one. Finn chose not to murder innocent people while Kylo did multiple times.
This is the fundamental problem I have with any Kylo Ren redemption arc. He had the chances, the means, and the support available to make a different choice, and he chose the darkness. Again and again in TFA, he chooses the darkness. FINN is the shining example of “it’s never too late to change” and Kylo Ren is the example of “ooh, a slippery slope, lemme grab a sled” (to paraphrase another post I’ve seen going around here lately)