You’re wrong, containerization is a massive security measure that shouldn’t be ignored. Proper containerization allows you to segment the namespacing of a single server by user and application; this helps massive with esrablishing boundaries that are still very difficult to cross under normal circumstances. Keycloak is an IdP which only provides one layer of security; good swcurity implements defense in depth where every layer of the system has securiry measures. Just because Linux recently had two vulnerabilities that bypass a lot of those doesn’t mean they’re worthless; you still need initial access to a nonprivileged user to exploit those and layered security can help prevent that from happening in the first place.