According to the FAA it was needed.
The 737 MAX was designed to handle and feel the same to the pilot as the 737 NG. Without the MCAS function, in some small areas of the flight envelope — such as approaching a stall and during higher g-force maneuvering — the new engines contribute to the control column feeling lighter in the 737 MAX than the regulations allow. These are not areas of the flight envelope in which the airplane normally operates. However, FAA regulations, specifically 14 CFR 25.143, 25.201, 25.203, 25.251, and 25.255, still require the control column to have a higher pull-force feel in these flight regimes than would exist on the 737 MAX without the added stability from the STS and MCAS function.
For the FAA to certify the 737 MAX, the original design had to meet FAA requirements for control force feel when maneuvering or deviating significantly from trimmed equilibrium. The aircraft manufacturer is responsible for making design decisions and showing compliance to applicable regulations. In this case, Boeing elected to include an additional flight control law in the STS, which is part of the flight control software that provides required control force feel to the pilot.
This flight control law, or MCAS, enhances the feel of the column forces in manual flight, and is only operative with flaps up. MCAS provides signals to move the horizontal stabilizer at elevated angles of attack to compensate for the aerodynamic effects of the 737 MAX’s larger and more forward-located engines, resulting in the required column feel to the pilot.
Source
https://www.faa.gov/news/media/attac...ummary-v-1.pdf (page 10)