It may be that you have apps running in the background (continually syncing, for example FB or messenger apps continually taking up band width to keep updated on news feeds), if you think that your settings are not much different than everyone else's then you could have a defective hardware that needs to be checked. UBreakIFix is he official repair center, so I suggest planning accordingly if you ever are near one.
One other thing you could do is to submit an error report on Samsung Members app after speed testing using Ookla's app. The samsung techs could confirm if it's the device's issue or a network issue (hopefully).
Additionally, as noted by others... the phone may be constantly trying to search for 5G when it's not available, which would take up a lot of power and result in slower performance 😕