A lot more core and leg strength will help a lot. You get tired easily with a lot of lurching.
Your arm and racquet preparation is quite inconsistent especially with the rear court shots - many times your elbows are very close to the body and not high enough. Normally a rule of thumb for rear court overheads preparation is to have the left arm raised to slightly above shoulder level and the right arm slightly lower than shoulder level.
Your footwork to the round the head position can be a lot smoother - you need a lot more sets of reps to that area to groove the footwork pattern. Gaining more leg strength would help this.
Quite a few times, when in the middle of the court, your arms are very straight downwards with elbows close to the body. Any particular reason for that?
I suggest going back to two corner routines with slightly slower pace but really concentrating on correct form. Then add three corner and then four corner routines. You’re not quite there for random four corner routines for regular training. However, as a diagnostic exercise with the video, it’s excellent for showing up the main areas to work on.
I second all of this, but in particular the RTH footwork jumped out to me. You had a few occurences where you didnt move in a straight line, but rather in a curve - first backwards, then suddenly sideways. This is ineffective - not only do you move a longer distance, but more importantly you had exactly the wrong pacing (first slow, then fast) and additional changes in direction, which take more energy than moving in a straight line.
At a short glance like this, it seems to me like 2 factors could be involved here:
1. footwork to the RTH corner is not instinctual - this you should really drill in shadow footwork, then add simple 2 corner exercise with the shuttle like Cheung already mentioned.
2. you appear to have some trouble either anticipating where the shuttle will land, or judging your position relative to it. Unless you're playing in an incredibly drifty hall, this is something more experience can fix - basically you need to see more shuttle flights so your brain gets better at anticipating them.
A general tip I touch on: in lower-paced drills like this, we like to focus on the correct pacing. It is usually more effective to push off hard, and then slow down slightly when moving towards the corner, because you won't have to spend as much energy reversing your movement that way. This holds true for all movements, including going back to your base: start quick, get slower as the shot allows.
By the way, good for you - sharing sth like this is not easy, especially if you feel like it isn't your best effort or you look a bit silly. Doing it anyway (ignoring ego and instead applying a growth mindset), and getting advice from the outside, are great steps towards improvement.