It’s probably the most tested and safest aircraft you can fly on. Keep in mind that both crashes occurred after transfer of control to very inexperienced copilots. In both cases the crews failed to manage thrust to keep the airspeed where you want it with trim issues. The MCAS system has been completely redesigned to prevent what happened occurring again. Certainly the system had faults that needed correction but this was far more crew qualification issues than aircraft issues. The copilot in the second crash quite literally had no experience.