I'm learning a bit of Classical Japanese recently, and of course the spelling of words is pretty different, due to sound changes over the centuries. For example, きょう was spelled けふ. That I can understand, since no language has static sounds.
I then went to YouTube and listened to a Japanese guy explain Classical Japanese. In the first lesson what he did was explain "historical kana orthography" and gave a whole bunch of ridiculous pronunciation rules. Yes, I understand that was how Japanese pronunciation changed over the centuries, but why should we emulate the sound shifts into Modern Japanese when we are reading Classical Japanese? What bad is there in reading いろはにほへと、ちりぬるを as "i ro fa ni fo fe to, ti ri nu ru wo" as it used to be pronounced?