A honest question. Could someone tell why is CSS getting more and more complex (other than Google and Co. want to protect their browser's market share and hold control of it)?
It's not getting more complex, because the easy stuff you have always been able to do is still there the exact same, as easy as it's always been. There is more of CSS now, so you have more power to express styles for more mediums in better ways, but you only need to use what you want so you don't need to make things complicated at all.