It’s been worth it for every trip we have done. We often finish ahead of the plan and have free time to do what we wish. The price is insanely cheap for what it provides. I have WDW, DLR, and Universal Orlando memberships and have done all of our family trips (listed in my sig) with them.
Despite how many people may know about TP, few people actually really use it. You always see anecdotal stories on here of families who refuse to follow the plan. I have never ever seen another person using the Lines app or using a printed copy of their Touring Plan while in the park.