Qurbani is an Ibadah (act of worship), and according to Islamic principles, there is no room for Ijtihaad (personal interpretation) when it comes to Ibadaat. They must be performed exactly as demonstrated by Prophet Muhammad (peace be upon him). Any Ibadah performed in a manner that deviates from the Prophet's teachings will result in punishment rather than reward.
The Noble Quran states:
"It is not open for a believing man or a believing woman once Allah and His messenger have decided a thing, that they should have a choice about their matter, and whoever disobeys Allah and His messenger, he indeed gets off the track, falling into open error." (Surah Al Ahzab, Ayat 36)
The purpose of sacrifice is not merely to slaughter an animal and consume or distribute its meat. Rather, it is to fulfill a religious obligation, honour the Sunnah of Hazrat Ibrahim (peace be upon him), and develop the virtues of Taqwa, Ikhlas, and a spirit of selflessness and sacrifice within oneself. The Quran itself clarifies this fact:
"It is neither their flesh nor their blood that reaches Allah, but what does reach Him is the taqwa (the sense of obedience) on your part. Thus He has made them (the animals) subjugated to you, so that you proclaim Allah's glory for the guidance He gave you. And give good news to those who are good in their deeds." (Surah Al Hajj, Ayat 37)
It is narrated by Hazrat Aisha (may Allah be pleased with her) that the Messenger of Allah (peace be upon him) said: "A human does no action from the actions on the day of Nahr more beloved to Allah than the shedding of blood (of sacrificial animals). On the Day of Judgement, it will appear with its horns, and hair, and hooves, and indeed the blood will be accepted by Allah from where it is received before it even falls upon the earth, so let your heart delight in it."
(Sunan at-Tirmidhi, Book of Sacrifices, Chapter on the Merit of Sacrifice, Hadith 1493, Dar al-Hadith, Cairo)
Furthermore, Hazrat Abu Hurairah (may Allah be pleased with him) narrates that the Prophet (peace be upon him) said: "Whoever is able to afford it and does not sacrifice (during the days of Qurbani), let him not approach our Eid Musalla." (Ibn Majah, Book of Sacrifices, Vol. 1, p. 226, Old Edition)
Implying that helping the poor is an alternative to sacrificing an animal is like saying someone who gives charity instead of praying or fasting will attain a greater reward. In reality, someone who helps the poor and needy by giving Sadaqah and skips their fasts and prayers earns the reward of the Sadaqah, but this also incurs punishment for missing the fasts and prayers.
In conclusion, sacrificing an animal during the days of sacrifice is obligatory. Giving money to charity or helping others in need is not a sufficient substitute for the blessed act of sacrifice. Engaging in these acts will not fulfill the obligation of sacrifice, and one would instead be considered sinful for not sacrificing an animal.