So, why bother with all that old tymie magic?
Some excellent points made. You wouldn’t use 2nd century engineering to build a highway interchange. So why use ancient magic?
A typical response might bring up the investment factor. Magical systems tend to function more effectively when reinforced by other users. Those that have been around a long time have been refined (edited?) to a high degree of reliability. The techniques can be easily taught and compared to other users’ experience. This is very valuable to a novice magicial.
Also, the exotic can be very effective to building an altered state of mind that better allows magic to function.
And then there is the question of what magic works on. If magic is a means of engaging a metaphysical system via the mind, then why wouldn’t an ancient system work? Has the mind changed so much in 800 years? The world we live in is different, as are many problems we face, but the means for engaging magical systems to solve those problems probably isn’t too different.
And we have no reason to believe that the magic of 800 years ago (or more) wasn’t effective, unlike the medicine of the day, which we know wasn’t. The medicine from back then wasn’t effective then, so it won’t be now. But if the magic was effective then, why wouldn’t it be now?
Now learning it properly, especially in a lost language, might prove tricky, and more effort than it’s worth. But that’s another matter …