I like your workout regime covering cardio, sprints, and calisthenics using the body weight for resistance which are similar to mine. Anyone undermining the wonderful benefits of walking must be from another planet. Humans evolved by walking. Its effects on the brain is noticeable and measurable. As you highlight walking is also meditative boosting mood as it can release beneficial neurotransmitters and optimize hormones. Thank you for walking your talk and sharing your experience transparently and inspiringly. Gyms might be necessary for those who don't have access to nature in crowded cities. It is better than no workouts. I still use gym for specific purposes as supplementary to my major workouts such as breaking my plateaus for weight training.