I don’t know exactly why they mean by that, but I think it’s a great time to actually say that DK does need a visual rework for most old spells.
After Legion, especially in BFA, some, almost all classes, received many visual reworks in their spells. Such as all the casters, paladins, monks and shamans recently, etc. Although DK is still one of the only, if not the only class that didn’t get any new sort of visual rework in old spells. Sure, the new spells are good looking, such as the hero talent ones, and the most recent ones like Abom. Limb, but most of the core spells of the class still have the same look they did back in 2008. I understand that maybe some people like it because of nostalgia factors, but it’s simply not fair that DK is the only class that didn’t get a visual rework. The class should, and probably will receive a visual rework in the future, but that has to be addressed.
We can take AMS as an example, it could look better, and Blizzard has done better already. Simply give us the Fleshcraft visual for AMS. Or make Fleshcraft a DK talent and do something different with AMS, but give us Fleshcraft back. And for the ones who like it the old way, just make a glyph like you did for the shaman’s Ascendance form. Death Coil should also look more nuanced, with more shadow in it. Something similar to Shadow Bolt but bigger and more impressive. Chains of Ice could also be reworked. Death Grip is fine but could also be reworked. As for DT, we already have the updated visuals for Monstrosity in Maldraxxus, just copy and paste it. I have seen some people saying they dislike the sounds of the spells, I don’t, necessarily, but I agree it could be reworked. The Lichborne’s lich icon that show when you use could also be updated to the updated version of lich NPCs in Shadowlands. More glyphs for the pet, there are many new undead mobs in Shadowlands that were never added as visual glyphs as pets for DKs.
DK seems like it has been strongly forgotten after WotLK. Giving DKs a fancy hero talent, as cool as it is, doesn’t solve the entire problem. There’s still more to work on here and it could have been worked on already back in Shadowlands.