[Wardad]

I have lost planets because the WPs do not have enough range.
Typically at equal tech levels the ships can move into WP firing range and Ships firing range on the same turn.
You may want to start with a Wall or Inverse Wedge formation and then let the ships break formation. Try to avoid a letting ships run up alone.
WP do not multiplex the targets very well, so it helps to have many targets. The default WP firing strategy can sometimes favor the biggest ships and ignore the smaller ones. So a smaller ship that is quick and hard to hit can slip in through the crowd. Load the ship with a Plague bomb or Planetary Napalm(s).