You're using the outdated fabric ID for Fabric API. Fabric API still "provides" the fabric mod ID for compatibility, but it's not clear what it is, so you should use the fabric-api mod ID.

Ref. https://github.com/StellarWind22/Fabric-Shield-Lib/blob/main/src/main/resources/fabric.mod.json#L60

The fabric-api mod ID is in FAPI versions for 1.18.2 and above.

Got it

Didnt know about this change, will do though! Is this just for 1.21.x versions or do previous versions also need this change?

Done in 1.21.3 and 1.21.4 so far