Whether people here accept it or not matters very little.Everything dies eventually.
That said, what you say is simply not supported by any evidence. There is no current evidence that a game must be able to support multiple genres, or it will die. Indeed, D&D, a mostly one-genre game, seems to be doing better than all the multi-genre games combined! At nearly 50 years old, the oldest name in the business, it has not significantly broadened its genre coverage, but appears to be selling and growing its player base to unprecedented heights.
So, maybe you need some better support on that idea before folks are going to accept it.
By the way, evolution, on the whole, does not drive creatures towards generalization. It more usually drives creatures towards specialization for a given niche. Invoking evolution, therefore, is maybe not your best bet either.
Modern Age and Modern Age: Threefold has a better thought out cosmology, and allows for use across multiple genres, deliberately so. And it is some stellar work by Green Ronin.
As to evidence, this is also false. Let's look at the number of 3PP releases that tap into different genres using the 5e engine shall we? The latest being Doctor Who. So all the support I need is to list the plethora of products.