The bigger problem is having people with the spiritual discernment to distinguish the two and considering RCC history, it seems that they're lacking in that area.
The one thing you missed in your comment about miracles, is that it's as likely as not that some of what people claim is just outright fraud to establish the RCC position beyond any reasonable doubt..... for its adherents.
The miracle needs to measured against Scripture to make sure that it doesn't violate it. Then it might be considered valid.
Having a vision or visitation of Mary to make a declaration like about the immaculate conception, to verify a catholic doctrine, is just a little too convenient for comfort.
Having a miracle occur to establish a doctrine which is otherwise unsupportable with Scripture is highly suspect.
That is what's done ,dear sister. The Church thoroughly investigates a miracle before one is declared
Having a vision or visitation of Mary to make a declaration like about the immaculate conception, to verify a catholic doctrine, is just a little too convenient for comfort.
The Immaculate conception can be traced back to the early Church
Here are examples
"He was the ark formed of incorruptible wood. For by this is signified that His tabernacle was exempt from putridity and corruption." Hippolytus, Orations Inillud, Dominus pascit me (ante A.D. 235).
"This Virgin Mother of the Only-begotten of God, is called Mary, worthy of God, immaculate of the immaculate, one of the one." Origen, Homily 1(A.D. 244).
"Let woman praise Her, the pure Mary." Ephraim, Hymns on the Nativity, 15:23 (A.D. 370).
"Thou alone and thy Mother are in all things fair, there is no flaw in thee and no stain in thy Mother." Ephraem, Nisibene Hymns, 27:8 (A.D. 370).
"O noble Virgin, truly you are greater than any other greatness. For who is your equal in greatness, O dwelling place of God the Word? To whom among all creatures shall I compare you, O Virgin? You are greater than them all O Covenant, clothed with purity instead of gold! You are the Ark in which is found the golden vessel containing the true manna, that is, the flesh in which divinity resides." Athanasius, Homily of the Papyrus of Turin, 71:216 (ante AD 373).
"Mary, a Virgin not only undefiled but a Virgin whom grace has made inviolate, free of every stain of sin." Ambrose, Sermon 22:30 (A.D. 388).
"We must except the Holy Virgin Mary, concerning whom I wish to raise no question when it touches the subject of sins, out of honour to the Lord; for from Him we know what abundance of grace for overcoming sin in every particular was conferred upon her who had the merit to conceive and bear Him who undoubtedly had no sin." Augustine, Nature and Grace,4 2[36] (A.D.415).
"As he formed her without my stain of her own, so He proceeded from her contracting no stain." Proclus of Constantinople, Homily 1 (ante A.D. 446).
"A virgin, innocent, spotless, free of all defect, untouched, unsullied, holy in soul and body, like a lily sprouting among thorns." Theodotus of Ancrya, Homily VI:11(ante A.D. 446).
"The angel took not the Virgin from Joseph, but gave her to Christ, to whom she was pledged from Joseph, but gave her to Christ, to whom she was pledged in the womb, when she was made." Peter Chrysologus, Sermon 140 (A.D. 449).