All good. But I pull from pre and post Vat II for my formation. Pre Vat II, 80% of Catholics went to mass faithfully on Sunday and holy days. Post Vat II only 20% of Catholics faithfully attend mass on Sunday. So what happened?
Stuff like liberation theology, and fake ecumenism to name just 2 factors.
Then there are wolves in shepherd’s clothing. I was at a seminary event and a bishop emeritus entered the conversation. We were talking about this very issue. I said 80% of Catholics are in mortal sin for deliberately missing mass on Sunday. His head practically exploded. He said to me you can’t say that. I said oh really? Actually I was stunned by his response. Then I quoted the CCC 2181 The Sunday Eucharist is the foundation and confirmation of all Christian practice. For this reason the faithful are obliged to participate in the Eucharist on days of obligation (Sundays), unless excused for a serious reason (for example, illness, the care of infants) or dispensed by their own pastor. Those who deliberately fail in this obligation commit a grave sin.
IOW grave sin = mortal sin. Just as I said.
Then I quoted the following passage from Hebrews
24 and let us consider how to stir up one another to love and good works, 25 not neglecting to meet together, as is the habit of some, but encouraging one another, and all the more as you see the Day drawing near.
26 For if we sin deliberately after receiving the knowledge of the truth, there no longer remains a sacrifice for sins, 27 but a fearful prospect of judgment, and a fury of fire which will consume the adversaries. 28 A man who has violated the law of Moses dies without mercy at the testimony of two or three witnesses. 29 **How much worse punishment do you think will be deserved by the man who has spurned the Son of God, and profaned the blood of the covenant by which he was sanctified, and outraged the Spirit of grace? 30 For we know him who said, “Vengeance is mine, I will repay.” And again, “The Lord will judge his people.” 31 It is a fearful thing to fall into the hands of the living God."**
That consequence, describes mortal sin to deliberately miss mass. A person dies in mortal sin they go to hell.