Some ways I could imagine addressing this and the problem the article talks about:
* Aim to make travel planning not easier (i.e. less time-consuming) but more fun. Treat the app more like a game or media app where users spend more time planning their trip by using the app in enjoyable ways. Put a ton of discovery and browsing ideas for things to do in it. Pinterest for vacations and activities. Basically Instagram, but with a "book this" button next to that pretty sunset photo.
* Focus only on the parts of travel that aren't fun. Haggling over fares, logistics, reaching consensus with travel partners, etc.
* Support use cases beyond just travel planning. If it's also a commute planner, or "what do this weekend in town" planner, it may get used frequently enough to stay in a user's mind.