That's mostly incorrect. In Maryland, like in most places in the country, the distribution infrastructure is controlled by regulated monopolies that buy power on the market from generators. Your bills separate out the fees for usage and the fees for distribution, and the Maryland PSC has to approve both.

Only allowed to charge “reasonable” usage fee means no other non-usage fee allowed or it is purposely designed to allow other kinds of fees?

Perhaps utilities should be state owned where any profits are used to offset the tax load on the citizens..