Having started with frontend as well because of necessity, I've realized people actually appreciate people with backend background working in frontend. Especially on complex UIs it makes sense to have people who are comfortable building complex features even if all details aren't clear yet. On the other hand, backends profit also from people with frontend-only experience.
In complex UIs it makes much more sense to have product and design people who are able to simplify it without losing value for customer. Actually, ability to have the same outcome with less hussle is added value. It is manyfold more important with mobile-first experience.
