As an actual economist, I can tell you the issue there is that most central banks do not actually have much room for intervention as they have had in the past. Interest rates, as a baseline prior to previous recessions, are already very low, meaning lowering them further will likely have very little impact on the financial markets. And extensive QE, especially in the current climate which would persist after any such degradation, would likely actually intensify the problem: various trade wars, mostly started by the US, higher indebtedness across the board than prior to previous recessions, savings rates very low (in some countries record low), county/provincial/state budgets operating on extremely fine margins in most developed nations (with their emergency/surplus funds having already been drained in the past decade), faltering growth economies like China, Brexit uncertainty (as well as other political volatility), and climate disasters further stretching the resources of many nations (a problem which will only likely get worse). The last thing you want to do is flood the markets with every holder of value currency *and* potentially devalue every long-term government investment vehicle available (their value *should* go up in that scenario, but they’ll be seen as risky, as each nation’s fiscal state will be even worse than prior to the last recession).
It is one of the main reasons most central banks have been reluctant to lower interest rates over the past year, even in the face of mounting evidence of a world economic downturn. I have been harping on about this for nearly 2 years (at times on here) and generally get skeptical responses, except from middle-to-low revenue business owners currently seeing revenues falling (especially those that produce luxury goods, as they are usually the first to feel the pinch and are rightly used as a canary in the coal mine) and those working two or three jobs to stay afloat (many participating in the much lauded “gig economy”, which is really just a sham front for externalising costs from profitable enterprises to the embattled “independent contractor”). The biggest mistake anyone can make right now is to take the whim of the stock markets as indication of how the economy is doing. All that reliably tells you is how well those that will likely be able to ride out any such downturn without much trouble are doing. Not that I thought you were doing that, but I just find so many believe the stock markets represent the overall world economy, which could not be further from the truth, especially in the last 30 years, when valuations have massively diverged from the revenue assessment model (which is also one of the drivers of our current predicament — the investment world has gone absolutely mad).
All of this is to say: the next downturn will likely not be a “recession.”