Because they don’t provide any breaks in traffic, high flow times can make it difficult for people living downstream to get out of their driveway
People with eyesight disabilities can have problems navigating them. Advocacy organizations would like them to use stop signs rather than yield signs, but this reduces the throughput of the roundabout.
A few actual problems:
If a driveway directly leads into a high flow road, you have a stroad problem, not a roundabout problem.