In the mmwave range transmitters will not have to transmit higher power levels. First because the use-case for this range is when there is NO obstacles to go through (it does not really work otherwise...), in short distance situations, and then also because beam forming will always be used.
> especially when the benefits of 5G to the consumer are so dubious
Benefits are not limited to browsing speed on your smartphone.
5G is designed to be able to handle massive number of connected devices (e.g. IoT), very low latency (e.g. self-driving cars, industrial control), and very high reliability (industrial control, etc)