To be fair Age of Empires II HD is a poorly optimized and buggy title, although it is fun and the biggest map size is hilarious. Run something like Morrowind/Oblivion on the same machine, then ask yourself why a refresh of a tile-based game from 1999-2000 runs so bad. And it's not just the largest map and population sizes that run bad from what I remember. To use that game to judge the performance of a £200-400 laptop is misleading. Today's £300 laptop is an incredible piece of cheap tech, and both AMD APUs and Intel integrated graphics can tackle many old titles just fine. Games with broad graphics settings help too.
Wow, wtf is this: "On April 15, 2015, developer Ryz0n announced a new expansion for the game." Maybe there's hope yet.