Pick another type of exercise
I feel like the reason I exercise on and off is because I don't love the types of exercises I've tried (mostly the gym). Sure, you can be consistent with the right habits, but maybe the most important thing is to find something you actually enjoy. Of course, if you want hypertrophy, it seems that strength training is still the best way to go, but maybe the gym isn't the only way.
1. Gym -> Elastic bands
There are products like the X3 bar of the Harambe bar that supposedly provide the same benefits as weight lifting, but with a simple kit consisting of a bar and elastic bands. I think it costs around $500 (which can be the cost of a yearly gym membership). I might be more likely to enjoy this, because I won't have to walk to the gym and, well, be at the gym.
2. Running -> Rollerblading
I really want to try rollerblading again. I have enjoyed running in the past, but I feel like rollerblading might be more fun. Plus, it trains your muscles and I hear it's easier on the joints.
3. Running -> Skiing
Seems like a fun sport. I have almost no experience in it.
4. Running and / or HIIT -> Krav Maga
5. Treadmill -> Running in nature
Running barefoot on the beach. That's nice.
6. At-home bodyweight workouts -> Kettlebell exercises
Kettlebells are fun.
7. Anything -> The same but with friends
8. Running and / or HIIT -> Badminton / Volleyball
9. Jumping Jacks -> Anything else
10. Swimming -> Rowing
I just checked, and I was surprised to read that rowing targets your whole body.
I should probably still learn how to swim better though, because I'm very bad at it.