VENICE, JUNE 10 -- Britain's urbane foreign secretary, Geoffrey Howe, paused as the end came today for the seven-nation economic summit and reflected on whether these gatherings have become a wasting asset.

A useful exercise in "international group therapy," was Howe's considered judgment. The leaders of North America, Western Europe and Japan profit from giving each other "solemn assurances around the table that they will try to do better" on economic policy in the coming year, he said.

The Venice summit, the 13th of the series, provided fewer clear winners and losers than previous gatherings. Because of the accumulation of political and economic burdens carried by these leaders this year, it resembled a reunion of the walking wounded.

In another briefing room across a shaded garden from the British pavilion, French President Francois Mitterrand also summed up the summit as an event that has become a necessary evil now that "propaganda has edged out utility" as its primary purpose.

The turning of the summit into a major international media event "has led the participants to try to show that each one has won something," causing boxing terms to be used to describe "knockouts" by one leader over another, Mitterrand said with an air of regret.

In closing press conferences before departing this afternoon, most of the leaders suggested they were relieved that combat had not been more fierce this year. President Reagan will meet reporters and leave Thursday.

Whether instinctively or by premeditation, the official delegations appeared to be determined not to allow their counterparts to look either very good or very bad.

Mitterrand, for example, won a reference in the final communique to a goal of seven-tenths of 1 percent as the amount of economic aid that industrial nations should give to poor countries. He brandished it at his press conference as one of the summit's major accomplishments.

He had barely finished speaking when U.S. Treasury Secretary James A. Baker III mounted another podium on another island across Venice's lagoon to remind American reporters that the seven-tenths goal was an old one adopted by the United Nations years ago, to which the United States attached little importance.

Canada's prime minister, Brian Mulroney, also got the simultaneous build-up, build-down treatment from his peers, who refused to go along with his determined efforts to get them to endorse a tough summit declaration condemning apartheid in South Africa.

Instead, they agreed to let Italy's caretaker prime minister, Amintore Fanfani, follow his reading of the summit's formal declaration with a rambling "summary of political issues" that highlighted South Africa.

While Mulroney was emphasizing at his briefing how the other leaders had joined him in rapping Pretoria, other delegates were pointing out that the statement was made in Fanfani's name and did not commit the other leaders to anything.

"We can't possibly go into depth in these discussions when we come together only for a day or two under this gigantic, manic security," West German Chancellor Helmut Kohl complained at his brief session with reporters.

While the temperate weather and spectacular setting of Venice helped soften its impact, Italian security was intrusive, widespread and intended to impress the security specialists from the six other nations with its efficiency and variety.

Kohl arrived here weakened by splits in his government and by U.S. pressure that led him to abandon his reservations about the U.S.-Soviet intermediate-range nuclear arms control agreement last week.

He spent most of the conference deflecting new pressure to adopt more expansionary fiscal policies, and did not seem to enjoy himself. Equally quiet on big issues was Japanese Prime Minister Yasuhiro Nakasone, who is due to leave office in October.

The other leaders reportedly were careful to avoid references to President Reagan's Iran-contra problems, at least in his presence.

Mulroney played one of the more active roles at the conference, possibly hoping it would help boost the extemely low popularity ratings the polls now give him in Canada.

In addition to pushing South Africa and agricultural reform, he staged a successful preemptive move to limit discussion of the Persian Gulf to diplomatic rather than military action.

Howe gave the closing British press conference because Prime Minister Margaret Thatcher, facing elections on Thursday, flew out yesterday after an overnight visit. Italy has national elections Sunday.

Even less visible was French Prime Minister Jacques Chirac, who shares power with Mitterrand but who apparently concluded that his insistence on sharing the spotlight with the French president last year in Tokyo was a tactical error.

He attended this year's working sessions, but stayed away from the press, leaving the stage to Mitterrand.

The French leader, who can be combative when he feels challenged in international affairs, appeared to follow the implicit live-and-let-live motif of this summit by declining to answer an American journalist's question about whether Reagan had been less assertive at this summit than others.

"That is a story I won't help you write," he said.

And while there was a general air of disillusionment among the leaders about the results "in comparison to what they could have been," as Mitterrand put it, everybody quickly agreed to get together again next year, in Toronto.