

I often go through this:
https://wiki.archlinux.org/title/Pacman/Tips_and_tricks
You can quickly remove all unused packages with this command: (from the article above)
pacman -Qdtq | pacman -Rns -
My arch install is many years old, I don’t feel the need to re-install.
If you can, try deleting all the partitions and re-create them using GPT instead of DOS (MBR) and see if it then shows the same. Also agree that you should make your boot partition 1G.