It's not that backstory is unnecessary, it's just that this is such a ham-fisted way to literally insert a backstory. I think, for example, the Imagineers having a backstory that guides how they design and decorate a location to be believable is a positive thing. When they just write fan fiction (as someone else put it) and paste it up in a way that it looks like they're presenting fan fiction, that undermines the believability of the theming.
I also honestly think this way of promoting inclusivity undermines the whole exercise. For example, the character of Alberta Falls is a nice way of creating more inclusive stories in the park. Presenting her with a CGI graphic that completely clashes with the time period in which her attraction is supposed to be set makes her stand out as an after-thought meant to make the attraction appear more inclusive. Similarly, it's positive to have a LGBTQ character represented in the park. Pasting up bios and graphics that look out of place on Main Street makes it seem contrived. On that note, Disney seems to have completely lost the ability to create period-appropriate graphics.