Two decades of OpenGL experience?, sorry we are looking for someone with Vulkan experience. Two years of OpenGL experience? when can you come in?
It's the stagnation that leads to lower job offers. You need to convince me that you were a dedicated employee for 10 years (which you are), but you also need to show that you're willing to learn something completely different. This can be a side project (doesn't have to be crazy, but slightly more then just going through the tutorial), certification of some sort, or _something_ that tells me you're not just going to write java-esque rails.
I would even go so far as I prefer people with diverse backgrounds, who are really willing to learn, so that we benefit from mistakes they made at previous employers.
Have you actually had examples where this wasn't the case? This seems like a common sentiment that I myself have thought, but I honestly can't think of a single instance where a candidate with good experience or knowledge wouldn't actually be willing to learn something new, or wouldn't model code they write along existing idioms.