One difference that may possibly affect the strength of your argument is that fentanyl is a physically addictive drug. Social media may be "addictive" but they aren't addictive. If you genuinely believe they're equivalent, use social media for a year, and fentanyl for a year, and see which is easier to quit.
Actually, scratch that: make it a thought experiment. But if you can see that they aren't equivalent, you can see that it's not a good comparison.
One difference that may possibly affect the strength of your argument is that fentanyl is a physically addictive drug. Social media may be "addictive" but they aren't addictive. If you genuinely believe they're equivalent, use social media for a year, and fentanyl for a year, and see which is easier to quit.
Actually, scratch that: make it a thought experiment. But if you can see that they aren't equivalent, you can see that it's not a good comparison.