Holdo's Sacrifice Opens a Plot Hole?

In the scene where Holdo 9/11's the Mega Destroyer, does that open a plot hole for future installments? If a single ship can take down a Mega Destroyer, why not program ships to auto-pilot into massive ships at light speed? Having that as an option and choosing not to take it might be seen as a plot hole now. Heck, even if it requires a single pilot, better to sacrifice one than dozens in a frontal assault (as seen at the beginning of the movie).