The greyed-out JAR files issue in STS/Eclipse Data Source Explorer is a common problem.
Try installing the proper database tools:
Go to Help → Eclipse Marketplace
Search for "DTP" (Data Tools Platform) or "Database Development"
Install the Eclipse Data Tools Platform plugins
Restart STS
Try adding drivers again via Data Source Explorer
The newer versions of STS might have issues with the legacy Database Development perspective. so try above steps and let us know whether it is working or not.