I'm no doctor, but if indeed you have models you didn't create and it will be unreasonable to try and fix the mesh, for a flat surface like that the handy Cubic projection setting would work even if the topology is bad. Usually. Just have to adjust the scale to make sure it's right.
This example is a little extreme, but it's a Cosmos rug object, made editable and stretched quite a bit. The topology isn't bad necessarily, but by stretching it creates long triangles. The carpet is from the library. On the bottom is the material set to follow the UVs. Not so good, a little different than your issue. The top is the same object and the same material set to Cubic. Since there isn't a specific need to follow those UVs (which I struggle with) on a flat surface, it's a much quicker solution in many cases.