Can Irish permanent residents not move freely to other EU countries?

Yes, the free movement of EU residents is based on the Schengen Agreement. Ireland and Britain did not sign the Schengen Agreement, so naturally they cannot move freely.

Schengen Agreement, 1985 15 On June 4th, Germany, France, the Netherlands, Belgium and Luxembourg signed an agreement (also known as Schengen Agreement) in the border town of Luxembourg. Its purpose is to abolish the borders between member States, move freely and live indefinitely.

The main contents of the agreement are as follows: 1. The signatories of the agreement will no longer conduct border checks on citizens; 2. Once foreigners are allowed to enter the "Schengen area", they can freely pass through the territory of the signatory countries of the agreement; 3. Establish a system of police cooperation and mutual judicial assistance, establish a Schengen computer system, and establish files of all kinds of criminals.