The chosen activating parameter for MCAS is AoA.
This probably makes good aerodynamic sense, but if the stability deficiency relates to airspeed - trim speed stability, stick force, then there should have been the alternative of using (dual cross-monitored) airspeed. Similar, but not the same issue, as STS.
Does the use of AoA ‘hide’ some other aspect; or is the range of trigger speeds / Mach, and combination with wt/cg best managed with AoA?