SELinux still offers a lot of additional protection in the case of RCE. There are literal examples of it working in the wild, e.g.

For several versions of the OS, this worked quite well, but once dual-sim devices2 started coming out, this became more problematic. Furthermore, when SELinux3 became common on Android, this became more problematic since the radio SELinux context that rild started with was too restrictive for the implant to function. - RoidRage Bootstrap Methods (https://wikileaks.org/ciav7p1/cms/page_28049453.html)