There are low hanging fruits which would have adoption problems but that can be navigated. However, there are very painful things like modern compilers which a

There are low hanging fruits which would have adoption problems but that can be navigated. However, there are very painful things like modern compilers which are massive undertakings for an old languages. It cost Microsoft 3-4 years to rewrite the C# compiler to be modern. But the benefit is a language server which keeps pace with the compiler and refactorings on the same AST (aka more stable/reliable).