I watched most of your video, focusing on the turning point in imp.
1. You went for rams instead of castles / trebs.
2. He focused on units that counter your own, and you didn’t really do a ton against his composition. At least not to the extent that he did.
3. Once your main army died, you didn’t have enough production buildings to be able to reload your army. I would say this was the biggest issue I noticed is that you only had a few buildings that were actually producing units, especially close to the primary conflict area.
4. In castle age when you had a big advantage, you kind of gave up raiding. He then got counter-raids in on you because you were not doing anything with your own army. Not saying you should do things that jeopardize losing your army in that situation, but your units were hanging out by his base (unable to defend your own), but weren’t pressuring him to play defense.
5. I get the impression you started to ignore your eco late castle age or early imp as you started to focus more on attack. As a result, your vill count wasn’t as high as it could have been. That being said, you lost your army and momentum with over 3000 food in the bank and even some spare gold, so I don’t think this was the primary issue.
Not easy to do, but if you haven’t already, I would focus on trying to get more production buildings up and running, and then learning the hotkeys to be able to jump to those types of buildings and then produce common units. IE, have a convenient hotkey to jump to the next stable, and produce a gold unit (knight) or trash unit (scout).