I heard this explained this way.
And no one pours new wine (The good news of grace) into old wineskins. (the law) If he does, the wine will burst the skins, and both the wine and the wineskins will be ruined (wasted) . No, he pours new wine into new wineskins.” mark 2:22
(The law ruins grace, the mindset of the law ruins grace, it just can’t accept grace. Grace will make the law explode! ) You have probably seen them old wine skins explode before.
And since it is through God’s kindness, then it is not by their good works. (the law) For in that case, God’s grace would not be what it really is–free and undeserved. (grace = undeserved favor) Romans 11:6 since its grace everyone can come.