Sure, it sounds like propaganda to the average mangadex reader no doubt, but negative sentiment towards monasteries has never been unusual, even becoming mainstream at several points of history, typically during warring periods. And sure, there is plenty of room for debate and inspection, but to just wave it off as propaganda instead of an interesting, in-chatacter point put forward by the author is disingenuous.
This is even more ridiculous. The premise of the story itself is already clear that the manhua is meant to be a fluff story with fantasy elements, and the author is known to like the use of darker elements in the past to augment the fluff that the main characters currently enjoy. All of this doesn't even require you to know what living in modern day China is actually like lol
Religion in ancient China is not as straightforward as Christianity or similar branches in the US. I don't even remember which period Jianghe is supposed to be from, and I have no idea about the spheres of influence various religions hold in those times, but there can be hundreds of schools of thoughts and local religions spreading in China at the same time, especially when times are bad and people looked towards whatever gave them faith or which faction practically helped them the most.
Stereotypically, martial practitioners during times of strife favor Taoists who have a reputation of helping the needy over the Buddhists who have a reputation of shutting their doors to preserve religion. Obviously, it's just a stereotype so while it's common to see martial arts manhua and manhwa despise monks, it's probably not as black and white historically.
Regardless, my point is simply that it's not really out of nowhere per se and that your view of China's religious cultural heritage is true at some level since religion has been a huge influence at various points of history, but doesn't actually reflect how commoners in a mostly agricultural society would have lived their lives.
