I think SOLID is appropriate for the public interface parts of your code but the internals should strive for YAGNI/KISS. So the vast majority of your codebase

I think SOLID is appropriate for the public interface parts of your code but the internals should strive for YAGNI/KISS. So the vast majority of your codebase should aim to minimize lines of code and abstraction. Of course there are exceptions - sometimes you really do need to encapsulate complex sub-systems with abstractions but you should have a clear justification.