Understandable, but such is the nature of a game still in development. There are a multitude of visual novel games who do not let you rename the main character, and given the type of experience Password presents itself to be, this decision is more in-line with that. Visual novels as a genre holds no obligation to let you rename your main character as an inherent right, but it was very much a common feature during the early boom of them such as during Morenatsu era games.
It's understandable that you'd be upset when something gets taken away, much in the same way that it's understandable if someone isn't a fan of a revised character design or a new art style. It just comes with the territory of a game not yet completed still figuring out what it needs to do and be to present the best product. If this were a complete product though and I just outright patched the thing out? Yeah, that would be very hard to justify.