Can I avoid estimating backlog items?

Yes, you can achieve this by setting default estimates in a project. This means that all new backlog items will get those estimates by default. For example, use points as the unit, and set the default rough and detailed estimates to 1 point:

This way, all backlog items will count as 1 in release planning, sprint planning, burndown charts, etc. And you still have the opportunity to set other estimates, if you have backlog items that are larger or smaller than normal.

If you do this, you probably also want to configure the task estimation options in the project, to avoid having to estimate tasks. For example, select "No, don't estimate the tasks", "Manually enter the total estimate", and "Count the done tasks":