I think you are confusing ‘tradition’ with ‘law’.
The law said to keep the sabbath holy. Tradition dictated how the Jews thought that should be carried out - no healing.
It wasn’t a ‘tradition’ that said don’t drink blood, it was the law. Jesus came to fulfill the law, not to do away with it (Matthew 5:17&18).
So are you suggesting that we should all be following all 613 “laws” of the OT? The prohibition of blood is only part of Leviticus where a whole slew of other “laws” were located.
The key is that Christ did change things. Because He was God, He could. Besides, He wasn’t speaking of human or animal blood. He was speaking of His Blood. Some folks left Him for it because they were offended by it probably because of Leviticus; others did not. If He was speaking metaphorically, He could have easily cleared up the misunderstanding...but He didn’t.
It appears we still have folks who are offended by what He said.