What can be easily developed using the Lightning Component framework?

Customized JavaScript buttons are primarily associated with Salesforce Classic and are not the main focus or an 'easy' development target for the Lightning Component framework.

Salesforce Classic user Interface pages are built using Visualforce or older technologies and are not directly developed using the Lightning Component framework.

The Lightning Component framework, including both Aura Components and Lightning Web Components (LWC), is the foundational technology for building custom user interfaces in Salesforce Lightning Experience. These components are specifically designed to be easily incorporated into and compose Lightning Pages, providing dynamic and interactive user experiences within the Lightning platform.

While Lightning components can interact with integrated systems, the framework itself is primarily for UI development, not for building Salesforce integrations directly.