HFT is the true essence of trading--predicting short-term changes in supply and demand and acting accordingly.
> This used to give us a real picture of the public sentiment for those companies or commodities.
Can you pinpoint some moment when it stopped?
> Stocks are bought and sold in micro seconds
Most HFT strategies don't actually do this. Buying and selling in such a short period implies a pure arbitrage, of which there are very few. The ones that do exist are generally fully exploited by the single fastest participant.
> creating an unsustainable and unlevel playing field for the real humans in markets.
Depends on your investment horizon. The statement is nonsense for all but the shortest timeframes. In particular, the fundamental finance guys (the "investors") are in no danger from the machines.
> The current ecosystem is just unsustainable.
Why? Automated market-makers are a middle-man that temporally bridge supply and demand between "real" buyers and sellers. Kind of like a grocery store temporally bridges supply and demand between consumers and farmers. Kind of like a car dealer temporally bridges supply and demand between consumers and manufacturers. Kind of like... you get the idea. Why are equity markets different?