The sun drops 1000 watts per square metre on the people at the beach. The 5G phone signal is about 8 micro watts on the same spot. About 1 billion times weaker.
Furthermore, sunlight radiation is 5,000 degrees kelvin, 5G about 1 degree kelvin!
Sources
1 tennessee.edu 1000 watts
2 grandmetric.com 8 micro watts