Emphatically not.

Even deaf priests (the known cases are priests who lost their hearing through accidents or as they got older) could still officiate sacraments. By around 1400, the 1215 requirement that all Christians of both sexes had to confess their sins to their parish priests once a year was more or less actually in practice. Parishioners would sometimes levy complaints with the bishop that their local priest was too deaf to hear their sins, and could not assign the proper penance or offer absolution.

Moving on, I'll be talking primary about the Holy Roman Empire and the Dutch-speaking Low Countries. Some things are applicable everywhere.

The second problem with the assertion is that medieval churches were not the place where the Word of God was heard. First, for the most part, until the 15th century priests were not reading the Bible out loud in sermons--if there even were sermons, which wasn't always the case in rural parishes even in the 15th century. Kraftshof is my beloved example here. In 1402, the villagers petitioned their bishop to provide them a stationary priest (rather than one who traveled among hurches) to say Mass everyday for the good of their souls.

In 1431, they were writing to the bishop again, petitioning for a priests who had actual preaching skills.

But with Germany and the Netherlands leading the way (by a lot), the "Word of God" part of the equation had started to shift. Earlier preaching was not very Bible-centric (which is not to say it ignored scripture), but--for example--moral instruction was undergirded by the seven deadly sins. In 15th century G&N, the Ten Commandments crept into the mainstream as a parallel foundation for moral teaching.

The 15th century in G&N is also when instruction manuals for priests start to say essentially, "Read the proper passage in Latin and then offer an interpretation in the vernacular...but if you don't have time to prepare or to preach, just read the passage in the vernacular." It's even popular for wealthier bourgeoisie, gentry, and nobles to have (in their vernacular) books called plenaries, which are basically Bibles rearranged with passages in order by the standard reading on that date in the liturgical year. We know they would follow along during sermons and services.

Second, sermons were most often preached from the porch of a church, rather than inside. At least in Germany, this was after the Mass itself.

Which brings us to point three: how strongly visual church was. An early medieval pope called art the book of the illiterate, which may or may not have worked out that way in practice. But fancier medieval churches did have (often fairly standard) art depicting religious ideas or lessons, for example, people standing in an ugly-looking hell.

More to the point, the central focus of the Mass--of being in church--was the sacrament of the Eucharist. In 1215, also, the Church mandated that all Christians of both sexes (that's the language) also take the Eucharist once a year, on Easter. Other than that, the priest served as a proxy. So as Miri Rubin pointed out, the eucharist during public Mass was a multi-sensory experience to emphasize its importance. Incense, bells ringing, the priest elevating the host (Eucharist bread, which in the west was a wafer) above his head. It applied to all present.

Sharon Farmer and Irina Metzler, meanwhile, both point to an intriguing miracle story from the canonization proceedings for St. Louis in the mid-13C. A deaf man also named Louis had been raised by a blacksmith and his family (the Gauchiers), and as the miracle story asserts, he couldn't really understand the basics of Christian beliefs.

But when he was at St. Louis' tomb in the church of Saint-Denis, he entered the church like he had seen everyone else do, and knelt with his hands in the stereotypical praying posture like he had seen everyone else do. And as you can figure, he miraculously now had the ability to hear.

Now, we can't take this story at face value even in a mindset of believing in miracles. The crux of the story, from the perspective of making Louis a saint, is that Louis semi-Gauchier knew immediately that it was a miracle performed by a saint--even though he didn't know what a church was or a miracle or a saint or had any idea about Christianity. Nevertheless, we see what was a realistic idea of a deaf man creating a facsimile of the church-shrine-prayer experience the way he had seen others do.