Does ARDUINO UNO WiFi REV2 captures all the functions/features of ESP32?
Thus, if I have an ARDUINO UNO WiFi REV2, it wouldn't be necessary to have an ESP32 right?
A Uno+ESP8266 does not capture the feature set of an ESP32.
API Reference - ESP32 - — ESP-IDF Programming Guide latest documentation (espressif.com)
The Uno WiFi Rev2 would be more accurately described as "a Nano Every + ESP32" than "an Uno + ESP8266" because the primary microcontroller is the ATmega4809 rather than the ATmega328P of the Uno and its u-blox NINA-W102 Wi-Fi radio module uses the ESP32 rather than ESP8266:
But I do think your "does not capture the feature set" assessment is reasonable in general.
In the end, it really depends on the features @vulum is interested in. Just as the Uno WiFi Rev2 is missing features of an ESP32 standalone board, it has its own unique features (e.g., 5V logic levels).