What does "when" mean here? It doesn't seem like a conjunction that represents the time.
You are correct. "When" doesn't function as a conjecture of time in this sentence. "When" in this sentence functions as the word "because." Because our generation takes many photos, we need to change our outfits often. This sentence is similar to a conditional clause; if you do something then something else will follow because of that. If you take many photos, then you should switch your outfits often. Here are a few examples of "when" functioning as "because." Ex: When you are mean to others, they will be mean to you. Ex: When you exercise there are positive benefits.