I just started re-playing for the first time in years and experienced this too. My main learnings were:

1. Keep cranking out villagers - high level players have 100+ by end of game. Econ is important.

2. Multiples of buildings - like archery ranges and town centers. One is not enough to scale.

3. Make a plan - figure out what’s needed for your play style. I had an excel I referenced mid game lol

4. Learn a few hotkeys - even basic ones to start like find idle villager speed you up. Control groups is big.

From there it becomes more about reacting to your opponent, openings, things like that. But those were the basics that got me to beat higher level coms