People follow leaders for just two reasons ... tell me where we are going and help me to improve!

It is the "... help me to improve" element of leadership that appraisal is addressing. Before you can hold an employee accountable for their actions, the employee needs to able to perform the agreed responsibilities. The goal of any appraisal activity is to help the employee improve their knowledge/skill/attributes so that they can perform their current and likely future responsibilities to an ever improving standard ...

... appraisal is about helping people to blossom; about helping people to jump an ever rising cross-bar.

To help people blossom; to jump over the cross-bar, you need to understand:

Goals
What is involved in setting SMARTA goals, that is, goals that the employee sees as:

Specific | Measurable | Attainable | Relevant | Time-bound | Agreed

Roles
What are the activities that the employee needs to perform on a daily / weekly / monthly / annual basis?

Processes
Having established the "goals" and the "what" of the job, how does the employee actually go about doing the job?

Interpersonal relationships
Very few roles operate in a vacuum. This is more than common courtesy ... this is about how the employee interacts with and supports other people.