Requirements are a useful tool to direct the effort of a team of engineers in a productive direction. They don't have to be set in stone from the get-go - in fact, it's better if they are updated by different people as new information about your product becomes available.
This focuses discussions about when it is worth it to spend time micro-optimizing certain aspects of the system. If there's a requirement that you must consume less than X μW while in standby - then it may make sense to accept the increased complexity.
I agree that the problem is that the company doesn't seem to use requirements to guide the daily work. It should be easy to decide whether certain work is necessary - either you have a requirement or you don't.
Without requirements, people will always leave a trail of chaos in their wake as they do whatever is fun or good for their career and resume. The only advice I have for OP is to not be the sucker who acts as janitor for the messes they leave behind.
This focuses discussions about when it is worth it to spend time micro-optimizing certain aspects of the system. If there's a requirement that you must consume less than X μW while in standby - then it may make sense to accept the increased complexity.