I think I watched sister Boniface recently and gave up because several things were too jarring. One was modern attitudes and another was modern idiom, patterns of speech and accents.
I also didn't notice in things like Cadfael. (Note to self, rewatch this). I suppose I'm older now so notice the prevailing accent (eg upwards intonation and increased glottal stops. Not judging, just saying I notice.) It's safe to say that I know it's a made up world inspired by the past.
I don't mind made up stuff and I also like documentaries. What I can't watch is certain blends like scripted reality or faux history. I don't mind alternate timelines.
I also don't mind exploratory fiction and I don't mind something didactic. I don't like the one pretending to be the other. Like ideology masquerading as science. Or waffling pretending to be expertise (that probably belongs on the Shon/kumar/coco? thread.)