If you recently tried playing Age of Empires after playing later RTS games. you just realise how much you have taken for granted...
Campaigns that literally tell you what to attack and how through trigger and flares.
Auto farm replenishing, or no depletable resource sites. Lots of auto-micromanaging tidbits that you have to do manually again (putting villies to work, rebuild farms, selecting each building individually and clicking build...)
Counter units upon counter units, also units with special powers.
Playing in full 3D.