So why would Jesus proclaimed that out of 10 commandments God has given to Israel before, only two were considered as 'most important' commandments?
Does this mean to disregard the rest?
Actually no. In fact, all commandments were still imposed to the Christian era... EXCEPT... the observance of Sabbath Day.
Jesus Himself didn't observe Sabbath anymore:
For this reason the Jews tried all the harder to kill him; not only was he breaking the Sabbath, but he was even calling God his own Father, making himself equal with God.
John 5:18 (New International Version)
New International Version (NIV)
Also the Apostles:
One Sabbath Jesus was going through the grainfields, and his disciples began to pick some heads of grain, rub them in their hands and eat the kernels. Some of the Pharisees asked, "Why are you doing what is unlawful on the Sabbath?"
Jesus answered them, "Have you never read what David did when he and his companions were hungry? 4He entered the house of God, and taking the consecrated bread, he ate what is lawful only for priests to eat. And he also gave some to his companions." 5Then Jesus said to them, "The Son of Man is Lord of the Sabbath."
Luke 6:1-5 (New International Version)
New International Version (NIV)
This only shows that:
Therefore do not let anyone judge you by what you eat or drink, or with regard to a religious festival, a New Moon celebration or a Sabbath day.
Colossians 2:16 (New International Version)
New International Version (NIV)