A decent seat might open up in the few days before the flight, so keep checking.

But if only bad seats become available, you might be best to not select any seat. In that case the GA must assign it, and it often comes out of seats vacated by the last minute upgrades, which are almost always good seats.

Not having a seat is not much of a risk (other than you might get the worst seat on the plane, but that has likely already been reserved or assigned).