The ethernet adapter is not designed to be used with the iPad. The iPad does not officially support an ethernet connection, only wifi. There is no guarantee it will work, since its not something Apple consciously made to work with it.
The message is not that there is too much power, but that the device you are trying to use, the ethernet adapter, is using too much power, and the iPad cannot supply that amount of power to it.
Best way to get something that causes the "Uses too much power" message to work is to add a powered USB hub between the accessory and the iPad.
You need to realize this is not a supported way of doing this, so no guarantees it will work correctly or at all and that it will do so after iOS updates. It's a user found function that is not in any way designed to work like that by Apple and is expected to not be 100% functional.