Removed message icon from task bar. How do I get it back?

Engage jiggle mode (press and hold on an app), and drag the Message app back onto the Dock.

The Dock works similar to a folder. (Though I have folders in my Dock)

How to move apps and create folders on your iPhone, iPad, or iPod touch - Apple Support

Though not the case with Messages, here’s how to delete and to restore built-in apps:

Delete built-in Apple apps from the Home screen on your iOS 14 or iPadOS device or Apple Watch - Apple Support