I agree. If you want a mold-free liner, you’ll have to start washing it more. Here are a few other things to consider:
Make sure there is plenty of ventilation in your bathroom. The mold that grows on the walls and liner of your shower loves that humidity! Consider investing in a more powerful bathroom fan. You should leave it on for at least 30-minutes following a bath or shower. Also consider leaving a window or door open.
Use shower curtain hooks that don’t clip. These are the best shower hook because it’s less of a pain to get the curtain down to clean it. I can never go back to the ones that clip. My suggestion would be S-shaped or Omega-shaped hooks. The S-shaped ones are designed for a single liner, while the Omega-shaped hooks are designed for a curtain as well as a liner.
Make sure the shower liner dries completely. When you do wash the shower liner make sure it has the opportunity to dry. There was a reddit post some years ago that mentioned putting an empty laundry basket or two between the bathtub and the liner. That’s what I’ve been doing and it seems to work fine.