I don't know why getting the wrong affinity would stop them from getting it. There's no penalty!
But it does defeat the essential concept of the game.
Apart from simply being set on a new planet, there are two core defining propositions for BE: the Tech web, and Affinites. These are not merely features, like Virtues, the are game defining, both in terms of gameplay and in terms of what the game is about.
The concept of the tech web says "History is the past, it is defined, and recreating the past is a defined progress towards the present, so Civ gets a tech tree. The Future is not defined, we sit in the middle of a sea of possibilities, and our choices define where we will end up"
The concept of Affinities asks "What is the future of humanity? Do we spread ourselves across the galaxy, but in so doing always take ourselves with us, and use our technology to reshape worlds to suit a recognisably human pan-Galactic civilisation? Or in moving to new planets, do we adapt to each, and in so doing fundamentally diverge from our earthly roots, such that there would never be one recognisably common civilisation across the cosmos? Or do we move beyond these material choices, transcend our physical limitations and the physical pressures of our environment, and become uploaded consciousnesses, beings of thought and spirit?"
This is the story of BE. The tech web, as much as the planet, is the setting where the story is told.
The problem with a game mechanic where everyone gradually accumulates all the Affinities is that it prevents this story being told, and so defeats the concept of the game. It turns the game from a choice between distinctive futures into a steady progression towards a single, bland blended mish-mash. IMO, this is a big part of what lies at the heart of the criticism that BE fails to deliver on flavour, that it provides ways to achieve "+1 in something-or-other" without a real sense of meaning or purpose.