I think you’re looking at this through rose-tinted glasses.

In my opinion mounts, pets, toys or whatever don’t count as content, so in that case, you still get everything with the expansion and a sub.

But even if you think it’s content, back in the day you also already had Collectors edition mounts and pets, the stuff from Blizzcon (before it was digital), TCG codes, etc. Not much different than today I think. Have fun paying a few hundred bucks for a Zergling pet.