I think often times it depends on the game genre. Some do need to move on to keep interest, or to avoid the game becoming a solved equation.
Putting features in only when they're 100% ready will never work for a game that is developed in an iterative manner like SI does. Some future systems, maybe those not even on the 5-10 year down the road stage, need some things to be in place through other systems before they can come to fruition. Some are new things to the game but turn out to be a little underwhelming. Look at Starfield, as far as I'm aware Bethesda never had a procedural generation module/aspect to any of their games before. It's hardly revolutionary to games, but they've got that working in their engine now and I feel its fairly likely it will somehow come to use in the next Elder Scroll/Fallout games (probably to adjust caves & dungeons to have a bit more variation than the 10 or so tilesets they had before in different arrangements).