A traditional interpretation of the Lotus Sutra, among Buddhists outside of Tendai and Nichiren Buddhism, is that the sutra’s intent is to provide encouragement for those on the long, arduous journey of the Bodhisattva path.
When the Lotus Sutra says, for example, that anyone who goes into a temple or a stupa, puts their palms together and says “Namo Buddhaya,” has already accomplished the Buddha way, this is promising that one’s future attainment of Buddhahood is guaranteed the moment we first awaken to Bodhicitta, no matter how many subsequent lifetimes it takes to attain full Buddhahood.
What the Lotus Sutra is not promising is that we will instantly attain Buddhahood or even attain Buddhahood in one lifetime. The story of the dragon king’s daughter is the exception, not the rule, and is meant to provide encouragement for those who don’t yet have enough faith in their own ability to follow the Bodhisattva path.
In the vast majority of examples provided by the Lotus Sutra, Bodhisattvas attain full Buddhahood after many lifetimes of practicing the Six Paramitas, just as the Buddha himself did in many lifetimes leading up to his final rebirth: https://www.thoughtco.com/the-six-perfections-449611