No, that's how lidar works. Lidars have a single frequency and a very narrow bandwidth. Automotive radars have a bandwidth of 1-5 GHz. They operate around 80 GHz, which is very well reflected by water (including people) and moderately reflected by things like plastic. 80 GHz is industrially used to measure levels of plastic feedstock.
Compare TSA scanner images, which are ~300 GHz: https://www.researchgate.net/figure/a-Front-and-back-millime...
You are correct that most automotive radars like Bosch units [1] are very low detail though. Most of them don't output images or anything- they run proprietary algorithms that identify the largest detection frequencies (usually a limited number of them) and calculate the direction and distance to them. Unlike cameras and lidars they do not return raw data, so naturally when building driver assistance companies instead relied on cameras and lidar. Progress was instead driven by the manufacturers and with smaller incentives the progress is slower.
[1]: https://www.bosch-mobility.com/en/solutions/sensors/front-ra...