Accountability also needs to involve making sure people hold up their end of the bargain. I'm in gold elo. That might not impress a lot of people, but I worked hard to get here and I deserve teammates who have a decent attitude, are willing to put the team first, and who have the intelligence and skill of a gold player.
We can all have bad games, but there's a difference between a player having a bad game and one who just decided that because they aren't winning lane or even just aren't SOLO carrying the game, they are going to turn off their brain and not try. They aren't having fun because they're not the star/solo queue hero this match? They decide to intentionally ruin any chance their team has of winning, and grief while baiting newer players on their team into following them and ending the game as fast as possible by either getting your team to ff or losing.
The system, board, and mods/others in authority on boards all excuse such play unless it's old Tyler1 level blatantly obvious and spam reported by all 9 others in the game though.
If you are regularly losing perfectly winnable games because your teammates are doing this crap in over half your games - in gold elo mind you - and you almost never encounter it happening on your opponents' team then there is an issue. Matchmaking is unfavorably biased against you. And moreover, such players should not be allowed to play ranked and ruin everyone else's games just because they aren't carrying or winning lane - that doesn't give them the right to grief and ensure their team has 0 chance to win. All those things you listed: play safe, ward, help a different lane, be positive, etc... I try to do them and ask no more than that type of play from my teammate win or lose. And when all I experience game in and game out is griefing, flame, blame, harassment, and false accusations of "toxic" nothing gets done about it.
I'll be the first to admit that I have said a few things over the past 2 seasons which went too far and which I wish I had never said. That however is NOT the issue I'd discuss today. THAT issue is the fact that griefing is ignored AND this is true even when it is paired with other perpetual toxic behavior:
spam pinging legitimate item build and flaming player for their build
_spam ping someone's tp or ult when it wouldn't have made a difference or came available seconds AFTER a fight
flame someone for not bailing you out when you repeatedly make a stupid decision they warned you NOT to do and pinged you not to do
flame teammate for splitpushing when they can deal with enemy's attempts to stop them... such as 2v1 or 3v1... and refuse to do anything useful while teammate is pulling several enemies to their lane and giving you massive 4 man advantage (4v3, 4v2, etc.) elsewhere if you'd only take it; and if you STILL can't win, why are you forcing fight you can't win and then blame splitpusher for it?...and then go and do next point on list immediately after
go splitpush when you aren't equipped to deal with enemy answers to said push over and over (once is maybe just a mistake) at team's expense, flame team when you and/or they pay the price
act like kda or damage to champs is the only thing that matters in the game
and 100 other examples that I won't bother listing_
This stuff all gets ignored and/or excused in game. On boards, players and even mods respond with criticism towards the person pointing this stuff out rather than... yeah the system should probably be improved. "git gud" "you're just kda shaming" or "if you were good, you'd carry harder than they throw" or "you're being toxic" etc. etc.
So if someone - and rightfully so - is punished for calling a teammate an "idiot" or for telling them to "stop acting like a dumbass" then why the biased result of such a player facing that while another person can tell someone to "suck my *#A7" (paraphrasing last word) and nothing happens? Or someone play the opposite of how you suggest when losing or behind, grief away any chance their team has of making a comeback, harass their teammate(s) in game for asking them nicely to play how you suggest (safe, ward, etc.), AND say and ping hurtful, insulting, and/or toxic comments for much of the game and they are NOT punished? How is that possible? I can assure you it happens. All too often. And this is what I've been fighting the last 2 years or so to try to get changed.
Griefing mentality, give up and ensure your team can't come back because you don't like X about this match, under-the-radar toxicity/flame or harassment... it's all going unchecked and unpunished. And when a player goes to the boards hoping to have someone see common sense and galvanize some reform, they're met with more of the same. And when mods and others step in? They're attacking the OP and defending the toxic griefer and the broken system. That needs to change. You can't tell one person to control their actions and words perfectly while defending and making excuses for another person who is harassing the other one all game and doing everything in their power to make the game unwinnable. For one, it's poor business practice and invites only the most patient and saintly of people who (also) don't care about winning at all and the most toxic and vile of trolls and griefers to take over the population of a game which will inevitably lead to it's demise. More importantly though is that it goes against everything you should be standing for - protecting innocents, defending an honest player's right to have an enjoyable victory or loss, doing what is right, and improving the boards and the game. It's time to stop making excuses and start fighting for what's right. Just as you said... the above expectations you listed are realistic expectations for players even if they're losing lane or behind in a match as a team. To not even attempt such things or to flame and accuse someone of being toxic for laying out such advice in a positive, encouraging way should not be tolerated any more. Mistakes are mistakes and honest players learn from them, but people repeating the same bad decision(s) all game long are clearly not learning from them and are therefore not honest players truly trying to win and help their team. Let's stop lumping griefers in with honest players, sullying the name of honest players, and giving griefers a free pass.