Could you elaborate on this? Because I don't see any reason why Synthweaving & Armormech have no value due to the Cartel store...
On Ebon Hawk at least, I have made all of my millions off of Synthweaving. People underestimate the value of those orange schematics, especially for belts/boots/bracers. People want that stuff as they're leveling up, or to stick their endgame mods in for different looks. They take tiny amounts of often low level resources but easily sell for 20k apiece. Adds up really quick.
Augmentation Kit MK-6 are still selling like hotcakes for about 47k apiece, and purple augments are selling for around 70k each.
I just hate seeing a profession dismissed as worthless because you can't make one item worth 500k. There are different crafting styles and no right or wrong, just like anything else. I personally prefer to sell tons of cheaper things with minimal effort than have to grind and waste tons of money REing mods before I get anything worth selling for a huge profit lol.
Shadowlands GTN was flooded with so many cheap cartel armors, (belt, bracers are the only thing that sells now). MK-6 kits flux, seen them as low as 20k (way below the price of the materials to make them) there has been a run on them a few times (people like me notice this and buy a bunch) than by the next day prices are back to 45 - 50k (and people complaining that there are not on the GTN). As for arms, I stopped puting orange weapons guns on the GTN, no point picked up a cartel canon from my Republic alt for 15k (and it looks cool). I think every server is different, but for Shadowlands this is what I see.