Mistake or no "Matched Play" and points are designed for tournaments.
"You will find detailed additional rules for taking part in a tournament, as well as a comprehensive points-based system that assigns a value to every unit available in the Warhammer Age of Sigmar range." (Introducing matched play: pg 70 of the GH2017)
Narrative and open play have plenty of options that do not involve points... take a look at the armies section of open play on page 14 of the GH, points are just 1 of the 5 options offered.
Split the players into two teams, using one of the methods described below.
1. SELECTORS
2. WOUNDS
3. POINTS
4. CONFEDERATION
5. GAMES MASTER
Legacy armies from 8th ed often do not fit with the current Warhammer Age of Sigmar range... those that do are in battletomes and I don't see a problem with removing ones that don't fit.