LISBON, JULY 22 -- President Reagan's top Africa expert today described his talks last week with Angolan officials on Namibian independence as a waste of time that had dashed any hope of a new diplomatic initiative.

Assistant Secretary of State Chester A. Crocker said Angola's Marxist government offered no new ideas for agreement about independence for the South African-occupied territory or the withdrawal of an estimated 30,000 Cuban troops from Angola.

"Despite Luanda's earlier promises, no new proposals were made, no fresh ideas emerged and the talks were basically a waste of time," Crocker said in a televised news conference from Washington.

Crocker went to Luanda for two days of talks last week after receiving what State Department officials described as promises of a new initiative during discussions with Angolan Interior Minister Kito Rodrigues last April.

"There is clearly disunity within the Angolan leadership about the whole issue and I got the impression they had received no clear instructions from the top . . . . But the door is still open and we are ready for further direct contact," he said.

Washington, which supports the Angolan rebels, is trying to get South Africa to grant independence to neighboring Namibia in return for the withdrawal of Cuban forces from Angola. Angola has rejected such linkage.