It appears that your major problem is not Performance Appraisal but employee attrition. Your second problem could be a faulty organizational structure. Employee turnover could be due to various reasons, and one of them could be the lack of proper measurement of the work done. Quantifying the work helps in differentiating poor performers from excellent ones. However, to achieve this, you need to study the systems and processes of each department and then design the Key Performance Indicators (KPIs).
Performance Appraisal vs. Business Performance
The key point is that Performance Appraisal focuses solely on individual performance. We need to look beyond and measure business performance. To do this, you must have a well-designed policy on the Performance Management System (PMS). There was a query in this forum about PMS to which I have responded. You can view my reply by clicking on the following link:
https://www.citehr.com/511936-pms-company.html
In the provided link, you will find additional links. I encourage you to patiently go through each link as it may help you understand how the lack of proper work measurement is impacting your organization.
If you have any further questions, feel free to call me on my mobile number.
Thanks,
Regards,
Dinesh V Divekar