@rnai369 are you using the databricks free edition? Or are there policies where you can only create so many in your company?

The fact remains that you are constrained to a limited number in your situation. It's suggesting if you want to create a new one, you can delete an existing one (to free up the capacity). However, if you're looking for a different configuration for the warehouse, you can edit existing ones i.e. enabling/disabling unity catalog. 

@rnai369 Out of interest, how comes you want a new warehouse? 

You can have "Serverless SQL Warehouses" https://learn.microsoft.com/en-us/azure/databricks/admin/sql/serverless I'd probably advise using Serverless anyhow. 

All the best,
BS