What is the difference between Allah sending down the Qur'an and clear proofs to guide people and for them to enter Paradise, and people entering Paradise even if He had not sent it down, due to the absence of establishing proof against them?

The statement that those excused due to not receiving the message will enter Paradise is incorrect. The truth is that they will be tested on the Day of Judgment, as mentioned in the prophetic hadith (definition) about the four who will present their arguments on the Day of Judgment. Whoever responds to Allah's command will enter Paradise, and whoever does not will enter Hellfire. Guidance to the straight path is a great blessing that brings tranquility and happiness in this world and the Hereafter, whereas those who are not guided live in distress. The servant must appreciate the greatness of the blessing of guidance and thank Allah for it, and seek refuge from the whispers of Satan. For Allah Almighty has bestowed upon His servants messengers and books to bring them out of darkness into light.