Since everybody is implying it just takes time I can actually point out a few things that lower elo players struggle with normally as that may be a problem for you too.
1.
Make sure you are constantly creating villagers, 5 seconds of an idle TC in between vils leads to a huge disadvantage
2.
Make sure you get blacksmith upgrades before taking a fight, and get the upgrades as soon as u can, for example 15 knights with full castle age upgrades will kill 25 knights with no castle age upgrades every time (Hard AI gets upgrades)
3.
Make sure you aren’t Taking any fights up any hills, AOE2 has bonus damage for units attacking down hill, and deals less damage for units attacking up hill
4.
Get loom from your tc before clicking up to feudal age, it makes your villagers like 2x stronger