It's strange how this is quite recognizably an old version of English (bet the pronounciation is way different tho), but to actually understand the meaning of it you pretty much need a full-on translation. Even with the vocabulary provided, the grammar still throws me for a loop.

Trying to hew closer to the original grammar rather than preserve the poetry:

You know also that the forms of speech can change within a thousand years.

And words too, which at the time were prized, but now, shockingly foolish and weird we think them.

And yet they spoke them so, and succeeded as well in love as we.

A thousand years? That's so 1380 of you, Jeff! I can think of cringey '80s pick-up lines that fit this standard.

6 7

To anyone interested in the topic, I can recommend the excellent ‘The History of English’ podcast. It puts the changes in the historical context. It's chronological, so it's advised to listen from the start.