Listen, I’m going to go really slowly here for you.
If 1% of the playerbase is using addons, or 99% of the playerbase between both games is using addons, it makes literally no difference.
As long as the PERCENTAGE of the playerbase using addons is similar between both games, then you can compare the number of people downloading addons between games and get a fairly accurate idea of which game is more popular.
Here’s Recount:
https://www.curseforge.com/wow/addons/recount/files
Dec 11, 2019
8.2.5
257,386Dec 11, 2019
1.13.3
195,458
Here’s Bartender:
https://www.curseforge.com/wow/addons/bartender4/files
Dec 15, 2019
8.2.5
209,436Dec 15, 2019
1.13.3
167,041