Although I don't agree that fluorescent light makes a significant difference, the gym has long since worn out it's welcome for other reasons.
I don't like how crowded gyms are, especially at the turn of a new year. I decided to do bodyweight workouts at home for free. Pushups (one handed and legs elevated if they get too easy), bodyweight squats (single leg for more resistance), pull-up bar, planks. and jump rope (preferred for joint preservation) or running for cardio. These exercises will work every muscle in the body, plus they're easier on the joints from what I understand.
Why go to a crowded, expensive gym, where you often have to wait for someone to get off the equipment you want to use? Gym staff bossing you around, telling you how to use the equipment. Overzealous gym staff trying to sell personal training to you. Gas money wasted going to and fro, time wasted. In 2 seconds, I can get on the floor and do pushups, squats, etc.
I really don't understand why someone would pay to run on a treadmill when you can easily go outside, or just do jump rope.
A lot of people feel like they need barbells and dumbells to reach their maximum potential strength, but I don't think it's necessary.
I think most people go to gyms to get social activity.