What's your opinion on the take that Sam is always running away?
The short answer is I think spn's ethics are insane.
The longer answer is that if you did a rewatch and counted up all the times that Sam objectively "runs away" from a problem/his family/etc and all the times Dean "runs away" from the same, I'm not sure who would actually win. But I do think the narrative frames Sam as the one who runs, and that, over the long term, it treats "running away" as his cardinal sin.
For example, when Dean runs away from his mistakes in Road Trip, the narrative does frame that as immature and self-destructive, and punishes him with the Mark of Cain. But by s11, this is reframed briefly as a "we" problem in s11a (Sam: "if we don't change, right now, all of our crap is just gonna keep repeating itself") and then never held against Dean personally thereafter. Whereas Sam's equivalent attempt at running away--the s4 demon blood arc--continues to be held against him by the narrative until at least 13x21 (Cas: we let Lucifer out of the Cage.)
Even more interestingly, at least to me, with the exception of Stanford, the narrative also tends to treat Dean's episodes of running away from Sam as "abandoning" him, but Sam's episodes of running away from Dean as "betraying" Dean.
This is Dean abandoning Sam to his fate as Lucifer's vessel. The narrative punishment is extreme, but not only does Dean get a do over in the same episode and it never comes up again, but the quote is remembered by fandom primarily as a quote about how close they are. And I do think that's borne out by the narrative. If Dean abandons Sam, the world will literally end.
Meanwhile though:
When Sam screws up with Dean, he's betraying him. The problem isn't just that Sam is an addict or that he ran away from Dean's attempt to forcibly detox him for his own somewhat questionable "good", but that he did so with a demon whore. It's portrayed as a personal betrayal in a way that Dean abandoning Sam to Lucifer is not.
In some ways, Sam is even the more steadfast brother. He may physically leave Dean at times but he never stops believing in Dean's capacity for good. When it's his turn to lock Dean in the panic room because Dean gives up and runs to destruction at the hands of Michael, he doesn't do it. And in the Mark of Cain arc, he affirms that even if Dean kills him, he accepts it as necessary and still believes Dean is a good man.
Which brings me to spn's ethics and fandom's response.
If there's one single thing that spn is entirely, completely, one hundred percent consistent on, it's that tumblr is wrong. You can't just walk out; leaving is always wrong and will usually end the world. It's wrong if it's temporarily for the evening because you'd like to have Thanksgiving dinner and your family doesn't do that, or for four years because you want to go to college, or for forever because all your remaining loved ones have been killed before your eyes, or if it's only a partial withdrawal because you want better boundaries in the face of years of violence and autonomy violations. (To be clear, spn thinks the violence and autonomy violations are wrong too; it's just especially adamant that the only appropriate response is self-sacrifice.) The only reason Sam is finally allowed to temporarily leave in the finale is because he so obviously no longer wants to.
And all of this, to be completely blunt, is batshit fucking crazy. And I mean that in the clinical technical sense of the word. As a system of ethics it's an enormous mess, as a behavioral guide it's guaranteed to result in inappropriate assignment of blame and unnecessary suffering, and it's hard to interpret it all for me personally as anything but a response to trauma.
I do think that on an emotional level there's something wildly compelling about it though, and it's fiction, after all, so there's nothing wrong with it as a fantasy. The idea that if only you could prove your loyalty strongly enough your family would finally accept you, flaws and all, is an impossible wish many of us have spent a lot of our real lives trying to actualize. And seeing it happen on screen when it can't happen irl can be cathartic, much like revenge stories can be cathartic even though irl revenge is a terrible idea. The vibes are, in short, without flaw.
The thing that's hard for me though is remembering that everyone irl grows at their own speed. Not everyone is in a position to cleanly separate their emotional enjoyment of a plotline or theme from their intellectual calculus about whether or not it makes any fucking sense--especially when those plotlines or themes are about violence, betrayal, abandonment, and abuse. And it's hard for me to remember sometimes that huge swathes of meta aren't actually the result of [insert negative judgement here] but are just reflective of a different series of experiences than the ones I happen to have had.
Honestly I find it frustrating. I wish people would be better about separating out what the story is saying from what they think of that message themselves. I feel like the format of fandom meta is often kind of a disaster. It adopts an authoritative, academic tone, but is usually actually used to express personal feelings and wishes without acknowledging that it's doing that.
It's not that I think people should have to disclose their personal experiences to write meta--on the contrary, sometimes that's helpful but sometimes it just makes it worse. Rather, I wish people would get in the habit of using more "I" statements and acknowledging their subjectivity more overtly. Back in the days when dinos roamed the earth and I was an undergrad, I learned that the use of the third person passive voice in academic writing is a political choice. It grants the illusion of more authority and objectivity than actually exists. I wish fandom would take up my professor's call to abandon it to some extent and say "I feel hurt that Sam left Dean alone with John to go to college" rather than "Sam is always running away".