A few other issues to bear in mind, the A52 does not support HDR or Wireless charging and the S21 has a maximum brightness of 1300 nits compared to 800 on the A52. I would say overall the processor and camera on the S21 are better but some features comparable and depends if worth it or not. For some Micro SD card and headphone jack are important. Can see some comparisons here https://www.pocket-lint.com/phones/buyers-guides/samsung/156187-samsung-galaxy-a52-5g-vs-samsung-gal...
I do not work for Samsung or make Samsung Products but provide independent advice and valuable contributions.
My Device- S21 Ultra 5G ( SM-998B/DS ) CSC= BTU , 12GB/256GB
One Ui 4.0,Android 12 Official Version.