No they aren't. Not all players are like that.
Some like me know how to build effectively, and always adapt to each game as to what I need more of (more armor if against all AD, or MR if the other way around, what CC effective items I might need, etc).
My mechanics are fine. Others might not be as familiar with the game to know them well.
I know the map rotation just fine, always ward as much as I can, and team comps are one thing that lower elos are not good at which is freaking frustrating as all get out but I try to do my best with it. You might get players that know they need a tank or juggernaut top with a good engaging jungler and then games you get a freakin Teemo top, Ezreal mid, Yi jungle and then leaving the support to be a tank. But I know what a good team comp needs to be to have a chance at winning.
I sure as hell know how to deal with enemy champions that pose big threats to the team. I ban them as much as I can but if one slips through I make sure I adapt. Blitz? Take Morg if she isn't banned and block his shield. Zed? Peel him away, exhaust, do whatever to protect the ADC. And on and on.
Attitude is just a part of people. I'm sure there are screaming, angry people in higher elos that think they could be even higher if they didn't have trolls, afkers, INTing, etc. But some have great attitudes that work with the team to help their chances to win the game.
Not all people in silver and bronze are like what you say. You need to be nice to people.