NETWORK television news, usually at its best and sharpest when there is trouble in the world, is in deep trouble itself.Modern communications have allowed independent stations to air their own national and international coverage, creating the impression in viewers that by tuning in to the networks on a given evening they are seeing and hearing news that is already old. The networks have also been hurt by the Cable News Network with its around-the-clock coverage. During the Gulf war, CNN became the news network of choice for a vast audience, leaving the three major networks and their highly paid anchors behind. That there will be changes in network news, and that these changes are likely to be drastic in the years to come - with the networks looking to pool their resources - is evident from recent announcements. NBC News has said that it will collaborate with the Public Broadcasting Service (PBS) for coverage of the 1992 Democratic and Republican conventions. NBC's anchor, Tom Brokaw, will team up with Robin MacNeil and Jim Lehrer of the "MacNeil/Lehrer NewsHour" to provide combined commentary. (All the networks will sharply curtail their political convention coverage which, in 1988, saw the network audiences drop considerably.) Mr. MacNeil, one of the most widely respected television journalists and interviewers today, said in an interview that the network news problems have no real solutions. "Network news employs a great many very capable journalists. Its fatal flaw is that they operate as part of a system which is forced to maximize its audience," he says. "The networks have created a show which gets into the tent at the same time all the uninterested, uninformed, and uncurious people, as well as the well-informed and sophisticated. It is an almost impossible communications proposition." MacNeil has a theory about the hurried pace of the network newscasts, frequently a subject of criticism. "Commercials became shorter and shorter as minutes and seconds became more valuable," he said. "At the same time, our producers of commercials are brilliant. They devised a new kind of video literacy that was very much abbreviated. "Everything had to adapt in pace, or else it would have seemed slow in comparison. The news shows can't be duller than the commercials and the entertainment shows around them." THE "MacNeil/Lehrer NewsHour," widely praised for its intelligent, in-depth coverage of issues and events, was actually created in reaction to the networks' tendency to speed up and trivialize the news, MacNeil points out. The conflict today among network news departments is between people who say coverage of news is a responsibility that should not be influenced by either costs or ratings, and others who argue that news - like any other network department - should have mass appeal and be profitable. As a result, network news has begun to look more and more like entertainment, borrowing from the popular "actuality" shows - like "America's Most Wanted" and "Rescue 911 that draw sponsor dollars as well as ratings. Chipped away by these different forces, network news is gradually changing shape. There are many who doubt that it will survive in its present form. The ratings pressure threatens to push the news out of its hallowed evening niche and to replace it with various entertainment programs. If and when that happens, the networks may end up simply "packaging" the day's news for the local stations, with the emphasis primarily on background and interpretation. These changes could actually usher in a new era in news and commentary, and alter the status of news programs entirely.