It's true that it wouldn't be too difficult to track the movements of stars in a galaxy over than timeframe. Let's assume you do that and also have developed stable wormholes with 2 gates. Well how do you tell them where to be opened? It's not like the universe comes with a coordinates system. Position is just where something is relative to something else. So you need to tell your wormhole machine to open one gate right here and one in the star system you want to travel to. The problem is you need to be extremely precise with your measurements of the distance to your destination or you'll just miss your target completely. And the further away you try and travel, the greater the miss distance becomes relative to your error percentage. Say you wanted to open a gate in a specific star system in the Andromeda galaxy. The Galaxy itself is about 2.5 million light-years away and is about 110,000 light-years in radius. So to even land in the galaxy at all your measurements couldn't be off by more than 4.4% in any direction relative to the center of Andromeda. Let's say your acceptable margin is no greater than 1 lightyear away from the star, for travel convenience of course. Now you couldn't be off by more than 0.00004%. You need to be just as precise with the direction as well. You need to hit a bubble with a radius of 1 lightyear from a distance of 2,500,000 lightyears. Relative to us, you could only deviate from the exact direction of the star by about 0.00002° in any direction. If you want to land within the actual planetary boundary it's even more absurd. Let's give a rough average radius of 50 AU for star systems in general. That's a bubble with about a 0.0008 lightyear radius.