God indeed demands sinless perfection. Absolutely! And that is precisely the reason each and every one of us needs Jesus as our Advocate before the Father. Those who trust in Him are clothed in His righteousness. Note the transaction that takes place in Zechariah.
3 Now Joshua was clothed with filthy garments, and stood before the angel.
4 And he answered and spake unto those that stood before him, saying, Take away the filthy garments from him. And unto him he said, Behold, I have caused thine iniquity to pass from thee, and I will clothe thee with change of raiment.
5 And I said, Let them set a fair mitre upon his head. So they set a fair mitre upon his head, and clothed him with garments. And the angel of the LORD stood by.
6 And the angel of the LORD protested unto Joshua, saying,
7 Thus saith the LORD of hosts; If thou wilt walk in my ways, and if thou wilt keep my charge, then thou shalt also judge my house, and shalt also keep my courts, and I will give thee places to walk among these that stand by.
8 ¶ Hear now, O Joshua the high priest, thou, and thy fellows that sit before thee: for they are men wondered at: for, behold, I will bring forth my servant the BRANCH.
Joshua's sins are discarded, cast away. God Himself provides the new clothes, His own righteousness. Joshua, after this has taken place, is then charged to walk in all the ways of His God. This can only be accomplished in the power of the Holy Spirit abiding in the life. And at the end, despite all that has taken place, the BRANCH, Jesus Himself, is set forth as Saviour.
God does not call us because we are good. He calls us in order that He may make us good. For by beholding we become changed. Destined to be transformed into His image. Recreated in His likeness, as Adam was before the fall.
The question we must ask ourselves in not " are we perfect?". but "are we willing to be perfected?".