The problem with that kind of advice is that doing those things (spending time outdoors, meeting new people) require
willpower, and being depressed, or anxious, or in a number of other states of mind,
saps your willpower, and therefore your ability to execute on any of these suggestions.
Practical suggestions are the kind of things a therapist will recommend when you do seek help: cognitive behavioral therapy, or pharmacological solutions. They're practical because talking to someone on a set schedule every week, or taking a pill on a set schedule every day, requires much less willpower than the things people usually suggest, but has effects which increase your willpower, and thus your capacity for attempting those other things.