From what's visible so far in the investigations Boeing (a) botched the MCAS implementation and (b) failed to train pilots on differences between the Max and previous models. Cure those two and the problem seems to be solved.
Why does anyone think this? The MCAS system rarely engages.
The issue is simply to make the stick behavior similar to the older 737s at high AoA. For an older 737, when you're pitching way up, you really have to pull on the yoke to keep that high AoA. The plane naturally wants to return to a neutral AoA, so you have to fight it. With the new design, the engine position keeps the plane from wanting to return to the neutral AoA, at least to the degree it did before. Hence, the 'stick feel' at high AoA is lighter. You don't get the same tactile feedback about being near a stall. (you still have the stick shaker)
The MCAS is simply there to bring back that resistance to extreme AoA, and thus make it less likely to accidentally stall. MCAS isn't even active with flaps down (i.e. around takeoff and landing) so can't possibly affect those aspects of flight.
It's a questionable design for a number of reasons, but it's not at all necessary for flight, let alone 'basically impossible' without it.
For Lion Air, the pilots didnt run (or even recall) the checklist so didn't disable MCAS.
However Ethiopian appears much worse, pilots did run the checklist, had some success with MCAS turned off but couldn't operate the manual trim (unclear why). They then made the fatal decision to turn back on electric trim (and MCAS with it) and MCAS almost immediately nosed them down into an unrecoverable state.
The Ethiopian airlines crew followed Boeing's post-Lion Air safety bulletin and still crashed. There's no safe way to operate a 737 Max in its current state. The hypothetical recovery techniques (e.g. point nose down to release pressure on the horizontal stabilizer) only work at high altitude, which is notable if Ethiopian airline's AOA sensor was damaged by a bird strike right after take-off.
Nobody who understands the current state of this investigation should be saying they'd be comfortable on a 737 Max without changes. The "pilot training" narrative isn't just dead, but dead, buried, with a tomb stone.
Sure, pilots should have received training on MCAS existing, but MCAS was commanding trim changes that aren't easily recoverable under any circumstances and certainly not if you follow procedure and disable electronic trim. Nobody should fly on the 737 Max until an update completed, I'd go so far as to suggest that the US/EU should ban ferry flights.
That's not quite right. Manually operating the motorized trim as soon as unwanted nose-down trim is detected prior to disabling it with the cutout switches appears to be a viable means of recovery. It's also an undocumented, timing-sensitive procedure in a critical phase of flight, which is not anything resembling what airline pilots want from their planes.
That's what the Lion Air crew did. They died. The Ethiopian Airlines crew followed Boeing's safety bulletin. They also died.
But I do take your point, which may prove to be correct. It is hypothetically possible to electronically trim against MCAS then immediately cut out the electronic trim system before MCAS has a chance to re-initiate (5 secs after last trim command). Then you mechanically trim for the remainder of the flight, which should be possible without too much pressure on the horizontal stabilizer.
It is crazy to think that that may ultimately be the life saving procedure here, given its complexity/nuance. Particularly for a largely undocumented (for flight crew) system.
I find the design of this system shockingly ill-considered. At the very least, it should require input from both sensors and not activate if the sensors disagree. It seems to me a better system would be to automatically add some nose-down trim if the pilot applies full forward pressure on the stick since the primary underlying concern is insufficient elevator authority in certain impending stall conditions for that standard pilot response to be effective.