Cool on not needing the others 👍
But RCS is a standard and recommended to use, for both QoL, but also security. SMS is less secure and means chats with family aren't E2EE. So unless you use some sort of other communication method like the Signal app, WhatsApp (w/ E2EE enabled), Threema, Matrix, etc. your chats aren't secure. Privacy is a whole separate question, and depends on your provider (i.e. Whatsapp is owned by Meta, which is the worst company for privacy.)
Please use RCS, or some form of E2EE