With minimal usage of samsung galaxy s21 plus after 2 years of use the battery isn't lasting that lon. It hardly last for 2 hours after full charge. Phone starts to overheat during 10 mins of video calls even with AC running in room temperature.
It seems that your battery backup is only 2 hours, which indicates that your battery may be damaged. You should visit an authorised service center and replace it as soon as possible. To check if any software is causing this issue, you can also try turning on safe mode and monitor the battery performance.