It is a controversial topic to be discussed. Will Azure Blueprints replace ARM Templates or Bicep? Well, we have been asking too much from ARM Templates. It can be very complexed, not just from the language perspective, but from the organisation perspective. Bicep solves the language complexity, but building a large infrastructure with many policies is always a mess. We can combine ARM templates but chances are multiple teams work in different ones if it is a large organisation.
Azure Blueprints are for managing all the deployments you need for one or more subscriptions at either subscription level or management group level. In a larger organisation you may have defined your management groups based on different requirements. It can be by environment type such as Dev, Test, Prod or by business unit such as Finance, IT, Marketing.
Different levels of organisation resources may need different levels of access. They all can be defined via the Blueprints. If need, permissions can be locked so only blueprint can modify them. ARM templates/ BICEP templates will remain as the deployment module in Blueprint so they can be changed and redeployed when in need.
You can simply start creating a Blueprint by going to the Azure portal.