You have to click so many buttons, check back and forth between traders and flea prices, it is an absolute nightmare of a chore when you have a big haul of items you want to sell and sometimes it can take as long as a full raid (when you sell a big haul you've been postponing for a while), which is simply ridiculous. I already expect someone to reply "well no one is forcing you, just sell to traders and forget about it", but that's the thing that it's just not true that you're not forced, when so many items return up to 10 times more value than selling to traders it's ridiculous to claim you're not forced. Yeah, you're not forced, just as long as you're okay with making 2-3-5-10 times less money per raid than everyone else. "Just sell only the most profitable items to flea" is also a ridiculous advice because there are so many items in the game and the values often go back and forth you can't remember all of this info, just checking the prices without selling will already take too long.
This was a rant, and i don't even have any thoughts on what "they should do about it". They'll undoubtedly do what they want and i just don't think any sort of qol would make things better, unless they completely automate the process, so that you can just click one button and let the game sell everything for you automatically, but it will either be unfeasible or ruin the flea altogether.