YuShan - I get where you are coming from but research shows that time spent "in nature" has measurable impact on mental health.
I read something interesting on the subject in a "blog" which I will try to re-find. I read it about 5 years ago, so apologies in advance if I can’t find it.
I found the blog following a visit to a nature reserve.
I was old, free and single at the time and took an Internet date for an outing to my local RSPB (4th date, so it was progressing). We enjoyed some decent exercise meandering the pathways but what impacted her view on the activity most significantly was the feeling of well being, calmness and mindfulness that over came her when we stopped at various points so I could show her the birds I was watching.