The thing is I feel like maybe you get more out of those 15 minutes than me, or others who feel like it's too much time. Those telling people not to use social media are probably the ones that don't have good experiences with social media. To each their own, I suppose. It's important to remember different people are going to have different experiences and that is going to paint your feelings about it. As much as it seems that social media does have a general negative impact on people, I'm sure there are people for who it is fine. Should we chastise everyone to stop? Probably not, just let others know it could be affecting them and how to stop, etc.
It reminds me of people who get anxious on marijuana and then always go anti-drug on other people because they think "this stuff is terrible, no one should do this" yet for a lot of other people they had great experiences, and so the reverse is true "this stuff is great, everyone should try this". They're sort of both wrong there.
Either way personally, I don't get much out of social media and so I don't use it. If you feel like you're getting something out of it worth those few days a year spent on it, go for it, although just be mindful that it's something that feels good, but might not actually be good itself.
That's not necessarily a bad thing though is it? I speak to my parents on the phone 1-2x per week for ~30 minutes at a time. That's 1-2 days a year just on the phone.