Feast of the Assumption of Our Lady

Today, the Japanese commemorate their unconditional surrender in WWII. Today, the Catholic Church celebrates the Feast of the Assumption of Our Lady. This feast has a long tradition and various churches celebrated this feast on different days. In 1950, it was officially proclaimed a dogma of the Catholic faith by Pope Pius XII, making use of the infallibility of the Pope for the first time. As a Catholic, of course, we rejoice in this elevation of this devotion to Our Lady. However, this action of Pius XII's created a huge obstacle in the ecumenical efforts with the other Christian traditions, including the Eastern Orthodox as well as the Reformed denominations. It involved the exercising of the Pope's infallibility which offended all churches, Orthodox or Reformed, and promoting the veneration of the Blessed Virgin Mary, which offended the Protestants. I have no clue as to why Pius did it. Since this event did not attract the attention of the authors of the New Testament, not even Luke, it is impossible to find any records in the Bible. Therefore, we can only leave all the theological technicalities to the big shots above.
Why should Catholics believe in this event, that after her death, the body of Our Lady was taken up (assumed) into heaven? Isn't the resurrection and ascension of Jesus, who is fully human, enough guarantee for our resurrection and ascension into heaven (assuming that we will end up in heaven and not hell)? What good/help does this dogma do for our salvation? I was baptized after Vatican II. The religious atmosphere has since changed. I do not think the local diocese or parishes have done enough to promote this Marian devotion. Though a Pope has declared this a dogma, I am afraid nowadays, not many Catholic know that they should believe in this article of faith in the same manner as the belief that Jesus is both God and man. I have not studied Mariology or any other branch of theology. Therefore, I am in no position to defend or explain this dogma. Since there are many Marian apparitions in the last two centuries. Therefore, I have no problem in upholding this dogma. But if you ask me to prove it, I have to apologize that I cannot.
I am happy to have a mother on earth and another mother in heaven. I pray to Our Lady to help my mother to kick her alcoholism. This morning, she started off well and ate one and a half hash-browns and half a Fillet-O-Fish. Despite her toothache, her appetite was good because she did not drink last night. She went to the grocers and prepared the dishes for meals. She did not complain about the relatives and cousins in our talks. Just trivial stuff. Good girl. Other than that, she did not do much, no knitting of cotton vests, no watching of TV. No nothing. She bathed and she took a nap. Around 3 p.m., she went out to buy two bottles of brandy (she intended four but brandy was out of stock). The atmosphere turned tense. We did not talk, nor looked at each other in the eyes when she entered the flat. She knew that I was not happy about it.
Yet, she was disciplined enough. She started drinking at 6 p.m., not 4:55 p.m. Tonight, she only drank one glassful of brandy, roughly one fourth of a bottle. That was not too bad after all. She knew she was addicted and it was not easy to kick the habit. She probably felt a bit guilty about it. To save her face, she said it was no good to cut it abruptly. She promised to wane it gradually. Throughout dinner, she repeated the same old stories of the hardship she went through. I would only echo verbatim what she said, instead of criticizing her. Yes, life was difficult. Yes, life is difficult. Yes, you were good not to abandon us. Yes, you were tough. Nobody could take advantage of you. Yes, the elderly approved of you, praised you. Yes, ... I became a Yesman. Dear BVM, what else can I do?

My dear Advocate, I thank You for choosing Blessed Virgin Mary to be the mother of our Saviour, the incarnated Son of God. She is blessed for her humility and faith in God. I believe that for our good, You have taken her, both spiritually and bodily, up to heaven before Judgment Day. She has the advantage of being full human. What You have done to her is a guarantee for what we will receive on Judgment Day. I pray that we may benefit from contemplating this glorious mystery. I pray for my mum that she may receive the blessing from our heavenly mother. Amen.