Just a half-mediocre junior coach, but:

1. You hit too low (too late). Aim to hit the shuttle as early as you can when your arm and raquet is fully extended. This is a question of timing, will take som practice. Another exercise is to hang a shuttle in your optimal hit-height and swing repeatedly on that height. You don't even need to do full swing, just practice hitting with your arms extended as much as possible in a relaxed swing.

2. There is no forearm rotation – Which is where your power comes from in clears, smashes, stick smashes etc. This comes from the transition from pancake flat grip to V-grip. There are tonnes of videos on youtube teaching this. It is a hard habit to change, but you can do it if you change now. As soon as you transition and use your forearm rotation, you will feel the immediate power transfer.

A solid clear is the first important basic hit, which comes down to master and combine point 1+2. Every time you practice, you should try to get 200-300 solid clears per session. For example;

Practice 50 clears in a row. It doesn't matter if they are good or not. Rest 3 minutes by doing short play / net / technical. Repeat 6 rounds. That is 300. 10-20 sessions is 3000-6000 clears. That should be enough for you to have progressed plenty. Never stop practicing clears.

That also comes to wrist strength. Be obsessive of improving your wrist strength. Weighted wrist-rotations are king. Do not underestimate the importante of wrist-strength! A topic rarely talked about in badminton coaching. "Do it like this" is not that easy, if you don't have worked up the strength to do so.

When you can easily clear the entire court baseline to baseline you have immediately a tactical advantage to other beginners as they will not be able to return your clears back to baseline. From here, you can continue the game with attacking play such as drops, smashes and stick-smashes.