Not every application running in your environment will be a "modern" one. Many companies still use crown-jewel applications like AS400. The best SSE platforms can use zero trust network access (ZTNA) to securely access AS400 - not only when an agent is deployed on the device, but also through an agent-less RDP session as well. Can your SSE vendor do that?

Learn more about SSE - https://www.axissecurity.com/what-is-security-service-edge/