While I agree it will be a step back for those apps lets also face the truth here: those endpoints were never meant to track realm population, as this kind of information is not publicly released by Blizzard itself since 2010 or around that year.
Personally I think it would be really great to have accurate realm population data, but I wish that information could be available for the realms endpoint or a specific endpoint.
Even if the AH endpoint still returned character names with the possibility of a character “hiding” their profile some statistics for realm population like class/race or even profession related data would be missing.
It would be really nice - and I know it is a huge thing to expect - to have a realm statistics endpoint. Something that would periodically return the amount of players, but also useful information like amount of characters that learned certain profession, amount of characters of certain race/class, amount of characters created per day over last X days, amount of characters above X item level, etc
That kind of information could really help players find the best realm to match their expectations.