Verbosity and architectural complexity matter to a coding agent. LLMs have limited context windows, and the less verbose the code, the more you can fit in there.

Complex architectures are even worse, again due to limited context. LLMs work well at the function level but have trouble seeing the "big picture". I would argue that working with agents is all about managing context and things like skills, subagents and the practice of writing plans are just a way to optimize context use. If you could stuff your entire code base in there with full attention, it would be much easier, but the costs of doing this would be prohibitive.