Glyphs serve a role as an additional 3 talent points for the last few expansions(less so for WoD, they have been gunning for removing it) that could alter our rotations and improve/lessen QoL in return for more/less efficiency, and now they are removing the system and replacing it presumably with the choices the artifacts give, except (correct me if im wrong), you can unlock all the weapon talents if you just get enough artifact power.
The way they have removed glyphs was a slippery slope we let happen, it used to be sets of additional modifiers to abilities we had to purchase to make our characters more proficient in certain areas, then they made them one time purchases, then they removed 3 of the 9 slots(remember medium glyphs?) then they moved all the glyphs to the prime size, and the minor glyphs became cosmetic, last expac some classes pretty much had no prime glyphs that were useful anymore, and now with legion, they are gone.
TL/DR they are essentially removing more things that let us customize our characters, at a time where Blizzard has said they value letting us express ourselves through our characters, I'm worried that Legion will ship with far to few things to distinguish one member of a class from another.