How do you ensure that features that your company launches are being used by the customers or not?

Your product team should have technology in place to record feature utilization metrics. In most of the places I've worked, when a new feature was put on a roadmap, it also included the feature adoption rate KPI.

Your goal as the PMM is to support the product team in achieving the adoption rate goal (assuming it was created using data and realistic expectations). To help improve the adoption rate of a new product and feature, you need to map out a go-to-market plan, which includes CS/Sales enablement, marketing activities, product updates and notifications, social plan, email plan, and more depending on the launch level associated with the feature.