No one, picking up a New Testament and reading it through, would conclude Mary remained a virgin. Neither would they conclude that Purgatory is real, that the Bishop of Rome reigns supreme, or that priests are needed to offer a literal sacrifice of the flesh and blood of Jesus each week (or more). Those require scripture to conform to tradition, rather than judge tradition in light of scripture.
He did plainly say, “Do this in memory of me.”
The Church Christ established on earth was sustained years and years (through Sacred Tradition) before any Gospels or NT matter were written.