The carnal mind cannot help but focus upon spiritual things with a carnal slant. "... which is exactly why everyone except the twelve Apostles left him, they refused to accept what Christ said." 'They' the devout Jews, believed that 'they' could have spiritual life of God by obeying the laws of God. What Jesus was saying to them opposed that prideful perspective and in inferring His coming death for them it contradicted what they thought He was there to do in the flesh, establish again the throne of David.
And Jesus used a metaphorical violation of the very law of God, a commandment to not eat the blood and to not commit cannibalism, as a meas to expose their false way to find salvation. That a catholic cannot see this clear use of metaphor and the disobedience tot he commandment of God to ALL THEIR GENERATIONS is symptomatic of the very same perspective in c atholicism. The spiritual meaning is contrary to their pride in self worth via their works of 'penitence' or 'righteousness' or 'charity' ... doe in the flesh not the spirit because they have yet to receive His Life, His Spirit into them by faith.
Talking about context and applying what is said to one specific audience as if it applies to all slaps Christ Himself in the face for what He said in the verses following John 3:16, verses Protestant folks ignore. If someone is already deluded into a heresy that denies the perfection of the Holy Spirit and preaches the same thing Korah was swallowed alive into Hell for I guess slapping Christ in the face is no big deal.
I would only digress slightly, by saying the carnal, unregenerate mind cannot focus on anything that is spiritual at all, with any kind of slant. Maybe that is what you meant? 😇