I used to feel that way but now I appreciate the usefulness of "% of time" concept for aligning individual or team effort.
For example, if my boss and I agree that I should be focused 80% on new business development and 20% on keeping existing customers happy, it doesn't mean I allocate every hour or every day this way, but it does mean that I pay a lot more attention to A vs B, but don't neglect B altogether.
That's a useful way to agree on what is important in your context so your work can overall reflect that.
For example, if my boss and I agree that I should be focused 80% on new business development and 20% on keeping existing customers happy, it doesn't mean I allocate every hour or every day this way, but it does mean that I pay a lot more attention to A vs B, but don't neglect B altogether.
That's a useful way to agree on what is important in your context so your work can overall reflect that.