Companies and investors look at the past experience of a candidate or an entrepreneur to determine if the person is right for the position or investment. This makes sense because you want to reduce risks as much as you can. Having people with concrete experience on something working on that something gives at least the feeling that they can do it well.
In the case of game design, this translates to genres and platforms. Companies look for economy designers who have worked on idle RPGs, for instance. Investors will probably fund ex-Riot people to make a new MOBA game for the US market.
But if you are a real game designer, you can work on different genres. I mean, if you know the basics of problem identification, audience, deconstructing mechanics, and so on, you can work on a platform game for PS5 even if you previously worked on casual match-3 games for mobile. We are not finding the cure for cancer, right?
In most cases, the only way of proving this capacity is alone or in a game jam. It’s hard to be hired by a company in a completely different environment. But the reality is that there are fashions, and maybe that popular genre in your area becomes uninvested, and you have to reinvent yourself.
How to do that? I prefer to start by applying my past experiences to the new challenges. The capacity to adapt insight and look at everything as a system is key. And it is a talent, so you need to cultivate it. I hold a design diary and often take notes of these cross-references and analogies.