I still see many people in Shenyang give their seat in the bus to the old, women with small children and pregnant women. I always do the same and I am middle aged and I get plenty of thank you's for doing so. I glare at any younsters who do not do the same and they can all tell exactly what I am on about. They either get up or look away for the rest of their journey. 
I am not sure what specifics of chivalry you are refering too. The example I have mentioned is probably one of the few which are actually better in China than in Australia.
Others such as helping accident victims are as we all know very much at the oposite end of the spectrum where it is almost the norm in my country and unusual here.
It all comes down to the examples that are set when you grow up, the values that your family, school, leaders instil in you and how your peers react to your behaviour that shapes these things.

NO! Of course chivalry's not dead in China .... foreigner's bring in plenty each year to keep it topped up!

TBH, and to counter Woody a bit, I think much that may be seen as 'chivalry' is actually an attempt to increase 'guanxi', or in others has been indoctrinated (not sure when, though, given the way kids act in this place!!! Who teaches them "respect"?) There is some level of respect given to some of the older folk (though in any given bus, maybe only 20-30% of the youth will actually give up their seat... or even move to make it easier for them to sit down). Because of the fawning over children, pregnant women, and those with young children will usually get a seat.. but again, it's still a 20-30%.

But, opening doors, holding doors open for someone, actually saying "Thank you" or "please".... nah....

actually, china traditional cultural told us"老吾老以及人之老,幼吾幼以及人之幼" that means  people should respect other's elder as respect as his elder, love other's children as love his children. we be told  help others who in trouble, but now the society security system  made us afraid to help ohters, that is irony,isn't it?

From what I've seen, there are people who are very polite (in Chinese terms) and then there are ones who are super rude. There doesn't seem to be many people in between. A part of it is also growing up without knowing how to use thank you or please, it just isn't the norm here. After seeing how some people raise their kids, I'm not sure why you'd question their lack of manners...?

I have wondered about this point for a long time. For example, the way they point with the entire hand, etc. seems to indicate thata there may (once) have been a standard for "good manners". Then I also hear that after certain events in the mid XX Centruy all forms of good manners and politeness were lost.
I guess my question is, were there better manners in the past (like 100 years ago) and if so, were they spead all over the social strata or were they limited to just nobility and scholars?

https://nypost.com/2021/03/05/texas-school-under-fire-for-chivalry-day-that-had-girls-obey-boys/

I wish they had this when I was young.