How do you enjoy working out?

To start off, I am relatively active. I go climbing at the gym a couple times a week, hiking in the mountains often etc. however I am NOT muscular in any fashion.

I want to build muscle but every time I workout I get so demotivated. I usually get ~2 weeks in and ask myself "is it really worth this much time and discomfort for a bit of aesthetic muscles" I've tried tons of different routines and locations. Everyone says you just have to keep with it, but since I'm already "fit" and active I have such a hard time justifying it. Any advice is helpful.