From my understanding, it’s not that Jesus didn’t sin, it’s that he couldn’t sin, by definition. Consider Mark 2:23-28 and Matthew 12:1-12, where Jesus and his disciples harvest and eat grain on the Sabbath. This would have been a severe sin under Jewish law – for most people – but Jesus is allowed to do it because “the Son of Man is Lord of the Sabbath.” Also, consider Matthew 5:22 – “Whosoever say, Thou fool, shall be in danger of hellfire,” – and Matthew 23:17, “Ye fools and blind”. (Both are quotations of Jesus.) There are a couple other examples of Jesus doing something which would be sinful for anyone else. But it’s not sinful for him, because he was, by definition, incapable of sin. (In the case of the Sabbath, previously sinful activities were made non-sinful because Jesus did them.)
The standards for sin were just as unrealistic 2000 years ago as they are now. The idea is that everyone has to be a sinner so they deserve to be punished eternally; thus, salvation must be attained through belief rather than action. Remember that God is willing to condemn people to an eternity of fire and suffering for telling a single lie, or thinking certain sinful thoughts. Even if a person were able to live without committing a single sinful action, any sinful thoughts might suffice for condemnation, and even if there had been none of those, you must still be punished because someone ate a piece of fruit 6000 years ago.