We just have to accept Sandhills is limited in what it can do. It can't deal with thousands of people at once. It's not like Stratford station for West Ham which is the 5th most used station in Britain now with multiple different tube lines and national rail - all with high train frequency and capacity. Sandhills is a tiny little backwater in the middle of nowhere only serving Merseyrail. A bit like Falmer by Brighton's stadium.
So we've got to look at numerous different alternatives to Sandhills to lessen the pressure. Train wise - walk to Kirkdale/Bank Hall (north ways). Walk back into town to Moorfields/James Street. But the elephant in the room is the occasions when Merseyrail is knackered then it's going to be chaos. Broken down trains are frequent, weather issues affect the service, signalling problems etc.
A lot of fans are going to just walk back into town, stay in the ground after the game, stay in pubs around the dock road. This is less of an issue on a typical Saturday afternoon, but on a cold/wet Wednesday night in February then that's a problem because none of these things are appealing.
That leaves buses. There needs to be loads of double decker buses within a 5-10 minute walk heading to town/Bootle.