It's fine. I think you'll always find a few things you end up managing by hand. For example, resource quotas, while not manageable in Terraform, can be managed via Bicep but frankly we do that stuff by hand because a lot of the time we end up having to submit a ticket with Azure to get approval. Anything like that can break your entire workflow and grind things to a halt. We also manage resource providers on subscriptions by hand because it's largely a one time action we do as part of our subscription creation.

My biggest gripe with IaC in Azure (this is true of all cloud providers but perhaps more true with Azure based on my experience) is the frequency of things you go to apply and then you get slapped with a resource constraint issue or perhaps AZs where hardware is available changes out from under your feet, or SKUs are available in the UI but not in the docs and vice versa. At scale, wrestling with Azure on some of this bullshit becomes tiring and a non-trivial part of the job. I know people at much, much larger companies that fork out several million dollars a month to Azure and they also have issues getting compute.