Some people are indeed studying how to detect lost steps and stalls without using encoders. However, these are currently only in the patent stage and are far from mature enough to compete with encoders. There is still a long way to go.
In fact, the use of encoders is the development trend of today's stepper motors. And if you want to implement closed-loop control, you must have an encoder or sensor to tell the controller the current rotation status of the stepper motor, so that the controller can make corresponding adjustments (accelerate or decelerate). This is the current state of technology.