I've now contributed to a couple of different blockchain projects, and I will say the MAJORITY of it is using existing development languages and frameworks. For example, underneath Golem you will find a codebase written in Python, and their bugs and issues are largely related to implementing business logic and integrating with 3rd party software like Blender which are not blockchain-specific problems. Then you have ones like Stratis which is effectively (at this phase) a port of the Bitcoin C++ codebase into C#. This requires more of an understanding of the functional adaptation between C++ and C# than it has to do with blockchain or encryption. I would guess that these kinds of problems make up over 80% of the needs of blockchain software development. Hope this helps!