A veteran Communist power broker, Mieczyslaw Moczar, was dropped yesterday from his post as chairman of a government watchdog committee, apparently closing the book on one of Poland's most shrewd, resourceful and ruthless politicians. The move coincided with several Cabinet changes announced by Polish leader Gen. Wojciech Jaruzelski affecting key problem areas of agriculture and the economy.

In a separate development, the itinerary for Pope John Paul II's tensely-awaited return pilgrimage to his homeland in June was released and showed that the pontiff will visit former Solidarity trade union strongholds in industrial areas in southern and western Poland but will avoid the northern Baltic port region around Gdansk where Solidarity was born.

The seven-day travel plan beginning June 16 was worked out by a joint Roman Catholic Church-state commission that reportedly never seriously considered Gdansk as a stop.

At a session of parliament that approved the government changes, Jaruzelski said Moczar, who will turn 70 this year, was being removed because of age from the chairmanship of the Supreme Chamber of Control. Moczar served as a powerful interior minister in the 1960s. An anti-Zionist movement that he ignited in 1967-68 led to a widespread purge of Jews from public life.

Jaruzelski replaced Moczar in the sensitive monitoring post with a favored Army officer, Gen. Tadeusz Hupalowski. Other Cabinet changes fell far short of a major reshuffle of the 36-member Council of Ministers and seemed motivated by largely unrelated considerations.

Agriculture Minister Jerzy Wojtecki was reported to have resigned to take a less taxing assignment for reaons of health. He was replaced by Stanislaw Zieba.

On another troubled front, the minister responsible for the new trade unions--which many workers have refused to join--had his portfolio expanded.