The translation you are using is not correct. Words matter.
Luke 18:19: " - - Jesus said, "Why do you call Me good? No one is good except One-God." NKJV. The ruler was addressing Him as if He was a mere man. Jesus knew: "all our (man's) righteousnesses are like filthy rags." Isa. 64:6.
In other words, our goodness/righteousness is not by following the law (which the young man was proud of), but in the Lord, is our righteousness. It was a lesson.
1 Tim. 2:5: "For there is one God and (no "also") one Mediator of (not" between") God and men, the man Christ Jesus." NKJV. The Lord Jesus was God from eternity (John 1:1). In time He became a man through incarnation (John 1:14). While He was living on earth as a man, He was also God (3:16). After His resurrection He is still man, as well as God (Acts 7:56; John 220:28). Hence, He is the only One qualified to be the Mediator, the go-between, of God and men. RcV.
I've already explained this back in the last page.
1 Timothy 2;5
heis - one. gar - indeed. Theos - God. = Indeed, One God.
heis - one. kai - also (in this context). mesites - mediator Theou - God kai - and (in this context) anthropon - mankind. = Also one Mediator (no conjunction in greek) God and Mankind. No conjunction means we take the meaning of the noun beforehand. the noun before hand means 'go-between'. Therefore the best course of grammar is 'mediator between', or else to write simply one 'go-between'.
anthropos - man. Christos - Christ. lesous - Jesus
Indeed, One God. Also, one go-between God and Mankind - man Jesus Christ.#
Indeed there is One God, and also one mediator between God and Mankind - the man Jesus Christ.
It really isn't significant whether it's 'between' or 'of'. It means exactly the same thing.
Similarly, in Luke 18:19, the word used for good, is 'agathon', the form of the word that applies solely to God. It is more inherent of our translation 'great'. It is 'intrinsic goodness', 'nobility' the quality only God possesses, that which God gives or 'empowers'.
The 'good' used in other ways, denoting humanity, has another word. When Jesus says 'I am the good sheperd', the word for good is kalos. And really, ask a greek. It doesn't mean 'good', it means 'worthy'.
There's a modern greek term like it. 'K'alos k'agathos' - the worthy and the noble.