And yet Jesus instructed the young man in Matt 19 to obey the ten commandments in order to enter life.
You are correct there.
During the first coming of Jesus to Israel (Matthew 15:24), Israel was still under the Law.
It will help to understand why Moses is the lawgiver, why the entire Law is summed up as the "Law of Moses", even though the Law was given by God.
Moses authority has been challenged before by the Jews, who wanted to hear directly from God instead. In the famous story recounted in Numbers 12
And Miriam and Aaron spake against Moses because of the Ethiopian woman whom he had married: for he had married an Ethiopian woman.
2 And they said, Hath the Lord indeed spoken only by Moses? hath he not spoken also by us? And the Lord heard it.
3 (Now the man Moses was very meek, above all the men which were upon the face of the earth.)
8 With him will I speak mouth to mouth, even apparently, and not in dark speeches; and the similitude of the Lord shall he behold: wherefore then were ye not afraid to speak against my servant Moses?
9 And the anger of the Lord was kindled against them; and he departed.
Thus Jesus himself referred to the Law as "The Law of Moses".
As he was living under the law, he was also subjected to Moses. (John 5:46, Matthew 19:8, Matthew 23:1-2, Mark 7:9-10).
So yes, obeying Moses, the Law, was required for Israel to enter the kingdom.
The real question you should be asking today is, are we Israel? Is Moses still our spokesperson, or is it someone else (Romans 11:13)?