For example, MoP has AoE looting: just one right-click and all the nearby corpses are relieved of their valuables (or organs as the case may be). I have seen some people in general chat confused by this change. "I can only loot one body!" But once this change goes live, all new players will consider AoE looting the norm.
Back in my day (vanilla), if you wanted to train all of your weapons as a night elf, you had to travel to Ironforge and Stormwind to do it. But there was no easy way to get there. That means you would run your level 10 self all the way from Darnassus to Ironforge via the Wetlands. Level 20+ crocolisks sure do think nekkid night elves are tasty. Yum yum. The key (other than having a higher level friend help) was to die strategically so that the graveyards would help you along.
If Tauren wanted to join the rest of the Horde, they had to run from Mulgore, through the endless terrain of the Barrens, and across most of Durotar to reach Orgrimmar. Ugh.
Don't even get me started about mount levels and prices. Anne Stickney covered the history of mounts and other ancient inconveniences in her article about how WoW has improved since day one.
And then of course there was Captain Placeholder. The boats to and from Menethil Harbor were unreliable and sometimes deadly. Happily, Captain P came to the rescue and ported us across so that we could survive the journey.
When you speak to new players who take their newish features for granted, do you give them an "In my day ..." speech? If you could go back in time to the self that first started playing WoW, what improvements would you say are coming that would have interested you most? What change do you wish had never happened?