You're spot on in that survival would only mean doing all this again next season. We've got players leaving even if we stay up, players that need to be moved on, and we've got raw players still developing. We would not be magically better next season in the PL.
The huge financial benefits of survival aside....If we could somehow magically guarantee relegation followed by promotion, that would be the ideal for the development of Stacey, Kelly, Ramsdale, Travers, Surridge, Solanke et all. Of course that's not how football works.