I am not a geek but POS is seeming like not having 51% attack problems and many POS coins are surviving till date without any major issues
It monopolizes the system.
Yes, it's the “rich get richer” argument again and yes, it's different with PoW. There is an actual procedure being done in PoW that requires computational work. You're essentially working for something to be proved. Being rich obviously allows you to buy/afford hardware and start mining, but it's not the same as sitting on your coins and getting even richer by doin' so. On a PoS cryptocurrency, it doesn't benefit you to spend your coins, but rather keep them.
You should understand how this mechanism rewards its users. Why would one be rewarded for proving that he owns an important amount of the coins? What did he do to be rewarded?
Bitcoin may not necessarily to adopt POS algorithm but may innovate and adopt something similar or superior to POS will help this earth remain greener.
Mining bitcoins isn't the first thing that comes into my mind when I think what really damages this planet. Roughly 0.6% of the energy waste is what Bitcoin does. Then, there are the renewable sources that are already used to a great extent.
There's lot of propaganda spread across the world about Bitcoin mining these days. Along with that here it comes the FUD.