Google Sheets is a tempting choice for a barebones CRM, especially if you're using the software in other areas of the business. There is no learning curve, it's free to use and may be sufficient for very basic needs.
That said, it's first and foremost a spreadsheet tool, and will lack any proper CRM features such as pipeline management, automated workflows, email ingestion, proper data security, and privacy. It's very easy to corrupt data if you're using Google Sheets for contact management, and there are no automations to keep it updated with important information, like email correspondences.
We strongly recommend against using Google Sheets as a CRM. If you're merely tempted by the simplicity of Google Sheets, check out folk instead. With folk, you have a minimal learning curve and it will offer you the basic features of a CRM like contact management, email integration and give you the ability to set reminders against contacts.