When I pacman-Syu, it fluctuates between 200kb to 500kb
I checked my internet speed at fast.com and it says 490Mbps
Something isn’t right.
Reflector is doing its job. I checked /etc/pacman.d/mirrorlist and saw the last updated time is very recent (today).
reflector will choose mirrors depending on your specific orders.
You have not specified your orders here, so I’m guessing you haven’t launched it properly.
Check the Wiki and launch it with your specific needs. Is it speed? Is it updatedness? Global mirrors? Local?