I would add that clubs, gyms, and meetups are a good, often free or very cheap option as well. Running, biking, skateboarding, climbing, calisthenics/acrobatics, board games, maker groups, art, music… all have very low cost of entry and likely have communities in any town or city.

I feel compelled to also add that while it seems well-meant, I think the tone of your last paragraph is a bit unproductive. A lot (most? all?) of us, at some point, fall out of the habit of exercising our senses of curiosity and wonder and trying new things. This can be caused by many combinations of family, economic, and social conditions, or for some, because of chemistry (ie “serious depression”). Therapy is indeed a good way to develop the skills to work against this and identify whether it’s actually a chemical problem in need of a chemical solution. But it doesn’t help to go straight to calling this “serious depression” needing “professional help.” Literally all of us can benefit from therapy, and making it out to be a big deal and putting labels on people makes many less likely to pursue it.