Why?

One more obstacle YACL needs to cross before it can become the de facto standard for client modding is cross-compatibility with forge. Countless mods that have showed interest switching to YACL already use Architectury, which limits them to libraries that also have cross-compatibility (unless they want a different UI per loader).

Problems

Architectury doesn't support split environment source sets

A feature of Loom that YACL relies on is split environment source sets. This allows for a clear split between client and common code. YACL utilises this with its config library which is available on all environments for mods that opt for json configuration on the server and a UI configuration on the client.

Forge's slow updates.

In the past, Forge has taken days to release a version for a new Minecraft version. On fabric, I'm used to releasing updates to my mods minutes after release. Depending on forge for builds prevents being able to push out Fabric builds because Gradle will fail because it can't find a forge version.