Whilst I have not had the S21 ultra that long I am impressed with the display, functionality, performance speed and overall experience. From experiments the camera is certainly an advance on S10 and seems to produce quality, though I have not used it in a real variety of settings yet. I am aware there are different opinions though and some problems may be sorted by resetting connections and clearing the cache partition.
5G is a battery resource drain with 5G really mainly improving how fast large files are downloaded.
Maybe change from 5G to 4G if your settings and Connections section allows this.
Current Phone > Samsung Z Fold³ 5G.
I am not often in a 5G area at the moment anyway , have the 4G setting selected.
I am still making up my mind about this phone. The camera "auto" modes seem just bad. OTOH, if I put the camera in PRO mode and turn down a few things like highlights, shadows, etc, then I can get good pictures. I have not yet looked at raw mode pics. As for the apps like phone and contacts, which Samsung puts instead of the google ones, I went back and installed the google ones as I am used to those.