It’s really hard to work quickly on a Minimum Viable Product when you don’t do both design and development.
A little design flourish might correspond to hours of development work which are not essential to getting the product to its minimal state.
At that point no one is to blame—the designer has made a good design and the developer has built to the spec. So ostensibly nothing has gone wrong.
Unless you understand both components, you can’t know whether your MVP design is truly minimal.