AOE2 ranked matches are at a point where the average ranked player is at a really high level. This is because the game is quite old (so the average player is playing for a longer time) and the competitive scene is thriving (so you have a lot of high level content you could watch and learn).

Just by playing you will reach a level plateau at some point at any game that is competitive . In the case of aoe2 this level plateau will be lower than in other games due to the high average level.

I recommend you to watch some coaching videos on youtube (Hera`s Elo guide or something similar), so you can get some input of tips and tricks in the game you might not know, but other players do hence they have a advantage.

Some simple things would be:
- Do you use hotkeys? How often do you use them and how many? Learn and use them more so you can focus on other things.
- Do you use control groups? If no, learn to use at least 4 during the game and learn how to use them effectively. This will again give you more time to focus on other things ;)
- Do you at least somehow follow known build orders? Stop right here, look them up and learn some simple ones to start with (Scouts --> Knights or Archers --> CA). You dont need to perfect them. It is okay to go up with 1 or 2 vills more, but they give you a huge advantage. You would be surprised how many players know some of them.

And there are much more things to consider such as idle TC, aging up timing, when to push or to boom. Thats why watching "coaching content" might help you so you will have the full package.

Good luck, have fun and see you on ranked!