Actually Keynes was right. But we need to take ourselves back to the time when he promoted this idea. He did later change his thinking, probably because he figured out the bigger picture.
His philosophy was developed at a time when we did not have a debt driven system. People, government and businesses had savings. Savings create a strong and resilient economy. However people will hunker down in times of stress and not spend which creates deflationary periods which clear out the weak, put banks at risk and government loose revenues. Those prepared can take advantage of deflationary periods, idiots dependent on handouts don't do so well. Anyway, Keynes idea was to trigger the release of pent up savings to initiate the recovery and reduce or eliminate the deflationary cycle. And since Keynes could not directly tell private entities what to do, the idea was to have government be the initial driver and then everyone else would pile in.
So the bigger picture is that, if you don't have savings in the economy to trigger, then what you are triggering is the acquisition of more debt. And if the cycle is debt >debt>debt rather than saving>saving>debt, pretty soon you get to the point where you can't even move the economy because so much debt is accumulated that there is no more expansion. One really has to look at 2010-2019 and ask who is going to take on the next level of debt to drive things forward. This is your red flag.
At least this is how I think Keynes idea should be viewed. I haven't read anything to this line of thinking because everyone keeps referencing Keynes without any reference at all to the nature of the world at the time. Context is everything whne talking ideas and theory. Government spending is good - Keynes said so - everyone know this - end of discussion. Well no, there is a bigger picture.
Exponential debt growth required to create the same economic activity as before.
Another red flag is the stock markets (not that you can call them free markets anyway), going higher each time the central banking cartel says something. Interest rates are said to go higher so stocks go up because all is well. Now ECB and Fed promoting lower interest rates. Why? Because things are not well. Unemployment is lowest ever, "inflation" (according to their fictional calculations) is stalled, economy looking like recession, so cut interest rates and what happens? Stock markets go higher. Yes, nothing says good times for corporations than forecasting an impending recession so buy now.
The reality is the so called free market system and stock markets is hinged on fiat scheme and cheap debt, not profit, revenues, savings, innovation or much of anything capitalist - but rather dependent on the central control scheme. And so we see both stock markets and gold going up at the same time. As I have said before - cover all the bases because in such a rigged game it is impossible to guess what will happen.