I am not sure where the idea that "we must be absolutely sinless" to be pleasing to God is found.
This is the understanding that Paul is addressing in Romans 2, and why it's important to distinguish between 'justification' (being made, or found to be righteous), and being saved (being delivered from the curse and wrath of God). Justification requires (someone's) perfect obedience. While the obedience presented at the judgment that 'saves us' (testifying that we have the righteousness of the perfect man, Jesus, legally applied to us) will not be perfect but will still be able to testify to the righteousness of Christ we have.
The point Paul is driving at is you have to keep all of the law to be justified by the law (Deuteronomy 6:25 Romans 2:1). As he shows them, no one, including them, does that. No mortal has ever done that. Therefore,
no one is justified by keeping the law. But you surely would be if you did/could keep it, just as his audience is sure they are doing, but, as he shows them, really aren't.
There's no such thing as a 'law keeper' who violates any part of the law (James 2:10-11). A 'law keeper' is one who keeps
all the law,
all of the time. No such mortal lives, or has ever lived (Romans 3:9-10). If you think about it you can see how ridiculous it is to think you're a good law abiding citizen because you drive the speed limit, but murdered your neighbor last weekend, and then somehow make a claim of righteous law keeping based on your driving record. But that's exactly the kind of appeal we humans make in regard to righteousness.
Righteousness is an all or nothing proposition. That's why we need Christ's righteousness. Which comes by having your unrighteousness wiped away and forgiven as a gracious free gift, and replaced with his legal standing of righteousness, not by the exchange of, or condition for, work accomplished...except the 'work' of believing, just as Paul says.
Justification is indeed by the 'work' of believing apart from any other work. Only the blood of Christ can remove unrighteousness. Believing in the blood to remove unrighteousness is how we access the gracious gift of that blood to do that (Romans 5:2 NIV). Any manifestation of that trust is just that--a
manifestation of that trust, not the actual trusting itself. Trusting and, say, baptism, are by definition two different things.
And it is absolutely insane to think that God instituted a Law that no one could perfectly follow - and condemn people to death if they disobeyed it, WHILE TELLING MOSES through divine inspiration, that it was NOT DIFFICULT to follow...
I can't think of anything in the law, in and of itself, that is somehow hard to do. What makes it hard and impossible to follow is the restless, rebellious, fallen nature of man. But in and of itself I don't think the law requires the impossible--just what is hard and impossible
relative to sinful man. What is hard and impossible, and 'wrong' about the law is man's inability and unwillingness to perfectly obey it (Hebrews 8:7-8).
Law, even a perfect law, is just so incredibly unfitting for a rebellious race of people as a way--a guideline--to right standing before God (justification). But the New Covenant--faith in Jesus Christ--
is the right and fitting way for a rebellious and faulty people to have right standing before God. The old covenant--the covenant of law--made no one perfect (Hebrews 10:1). The New Covenant--the Covenant of faith in Christ--does make perfect (Hebrews 10:14).