Evolution doesn't mean getting better: it means changing as the world changes

My teachers said that Beowulf was Old English/Anglo Saxon, & they really did say that Shakespeare was Middle English. I don't remember where they placed the Canterbury Tales.

Shakespeare was written in (early);Modern English.
The Canterbury Tales was written in Middle English.

Modern English began in 1400 or so AD. Your teachers were right about Beauwolf though, Old English.

I studied this at Uni. To learn a bit about comparing the different English languages, you need different versions of the same text. We compared bibles from different times, as i5 the most accessible (a public university). The Englis( language is now changing much more rapidly due to technology and greater literacy rates. Languages are more stable when they’re only read by a select educated few, and it obviously takes a lot more time to spread written changes when they have to be transcribed by hand and delivered by horse and cart. So the Gutenberg press and steam trains increased t(e rate of change in written English. Spoken English has always changed more quickly than written English for this reason. You could now argue that the internet has sped to change in written language to match the speed of change in spoken English.

I would challenge that "languages are more stable when they're only read by a select educated few" -- what's more stable is the written version of the language (as, for instance, written Chinese). The spoken language kept on changing and splitting, but the written records that we look at appear to show less change. Now, writing technology is easier to access and share, so we're seeing a broader swath of people using the language . . . personally, I think we have to think a lot more about sampling before we can compare the evidence we have for different periods.

Yeah, spoken language has always been more liquid and changeable. But I think now, with immediate communication of written changes online, written languages are changing at least as fast as spoken.
But now, of course, with live-streaming of video content, this is debateable

They also said that after reading Shakespeare for a while I would start understanding it. That never happened.

For a lot of people, it's seeing it well-performed that does it.

Oh, wow. They were just wrong about Shakespeare, then. The point that is Middle English is when the French and Anglo-Saxon roots are still doing the "enemies to lovers" process, before they blend more smoothly into the thing that is just English.

Another way of thinking about it is that the Old English is clearly Another Language (what even are some of those letters?), Middle English has recognizable bits but is often not comprehensible, while Shakespeare might have some words and idioms that we don't understand, but there are big chunks that you could just about hear on the street.