These are some concrete examples and ways to make delightfully boring software.
Adhere to the principle of least surprise, reducing cognitive load.
Focus on readability, for example in unit tests. It brings huge benefits and reduces complexity immediately.
Try not to over engineer, it is bad for a project.
Create what you need right now, follow the last responsible moment principle. Test driven development can help here as you only create what is necessary.
Simplify infrastructure, extra infrastructure and dependencies should be carefully considered. For example Micro services should not be the default.
Create self documenting systems.