hide old composition to avoid confusion

README.md

@@ -69,7 +69,13 @@ function and how it fits with other functions:
 
 ### Migration Example
 
-Given an example `Resource` Composition:
+Given an example `Resource`-mode Composition:
+
+> [!WARNING]
+> The example below is using the old native Composition Environment, which was dropped in Crossplane 1.18.
+
+<details><summary>Old Resource-mode Composition</summary>
+<p>
 
 ```yaml
 apiVersion: apiextensions.crossplane.io/v1
@@ -116,6 +122,9 @@ spec:
 
 ```
 
+</p>
+</details> 
+
 The above can be converted to use this function and
 [function-patch-and-transform] as follows:
 
@@ -254,4 +263,4 @@ $ crossplane xpkg build -f package --embed-runtime-image=runtime
 [function-go-templating]: https://github.com/crossplane-contrib/function-go-templating
 [function-patch-and-transform]: https://github.com/crossplane-contrib/function-patch-and-transform
 [go]: https://go.dev
-[upstream-docs-environment-configs]: https://docs.crossplane.io/latest/concepts/environment-configs/
+[upstream-docs-environment-configs]: https://docs.crossplane.io/latest/concepts/environment-configs/