How do I not get my ass kicked in AoE2?!

I recently downloaded AoE2 DE on Steam out of boredom and a bit of nostalgia as I used to love playing it as a kid. Thing is, I play it in exactly the same way as I did as a kid and I don't really know how to get better at it. I also feel like I'm not getting the most out of the game.

Basically, literally all I do is play in skirmish mode with full tech tree enabled and a big, fully revealed map (I tried a couple of the campaigns but I got a bit bored of them). I have the victory setting set to conquest but I rarely ever complete a game cos when I play on moderate difficulty, my empire gets too big and the enemy no longer poses a threat so I'm not gunna spend hours taking down every one of their units. So I ramp the difficulty up to hard and before long, I start getting my ass whooped so I just give up and start again!! It's either too easy or too hard!!

My general technique when playing is - always churn out as many villagers as possible and set them to gather resources immediately, build a block of houses, build a barracks, upgrade my empire to Castle age as quickly as possible, build archery and stable, guard tower and castle (and dock if applicable) and start building up an army. Then upgrade to Imperial age and continue gathering resources and upgrading units....you get the gist! When I have more resources I'll add an armoury and university and start upgrading my units more.

In hard mode, I can usually fend off the first few waves of enemies, but after a while I just get overwhelmed and can't fight back, by which time I don't have enough resources to quickly produce more units. I feel like I'm playing like a noob and missing out on getting the most from the game. Does anyone have any tips about how to basically play the game better?

Also, side note, I downloaded AoE3 and was super disappointed. It looks shit on my fairly low spec laptop and the skirmish mode has hardly any customizable setting from what I can see. You can't even choose a map...unless I'm missing something?!!

Sorry for the long ramble - hope you can help :)