Well, I played some maps for a bit with one of my old chars before the downtime and still as bad as always.
Desynced badly in a map boss almost gets me killed. This while holding the fire in place key with a damn bow. At least I know I won't be playing HC league any time soon again cause don't feel like losing my nth character to a necro in the other room lol, so all fine, gonna play casually in the SC league and try have some fun for a couple weeks at least.
The availability of gear and progression is balanced around trading. It's subjective how long it should take on average to achieve X or Y goal. But it's obvious that right now those averages are balanced around trading (and indirectly around the existence of pseudo-slave labour, aka bots), period.
For example, while getting a BiS (or close to BiS) item for a given build should be incredibly difficult, it could (or should, some people argues) be achievable by a single player. Right now it's not possible (on average, unless you are extremely lucky), at least with realistic expectations of time investment into the game. This is just one example of thousands.
The game experience is completely different, and GGG intended way for the majority to play the game (I'm not gullible, so they can say whatever) is with a massive pool of goods available through trading. Sure, you can play the game anyway you want, you can try to beat uber bosses naked even (not gonna happen), but self-restrictions or play individual play styles (as valid as they are) is not what game balance and design is about.
P.S: I didn't mention that trading shouldn't be the most efficient to achieve goals, as that's mathematically impossible the same moment you allow trading; but there is a lack of balance between different gameplay alternatives (hence the 'trading should be secondary' instead of the focus of the game for progression).
Trading per se is not the problem. Is the failed economic model that GGG follows with it's feudal economy which needs slave labour to be sustainable. Trade should not be the 'end-game', but an other alternate way to achieve player goals.
Also you can't design a good economy without consumption, so trade is always skewed and most goods fall in value over time, even in HC leagues which have more consumption (item sinks due to deaths). This makes for a poor environment for successful exchange of goods.
This creates a conundrum for designers in which they have to amplify the artificial scarcity so there is an opportunity for exchange for the individual (some goods still hold value) when the collective output is considered, but in doing so the individual player experience is damaged.
An other problem is that when you base your game around grinding instead of real challenging (and fun) gameplay you have to introduce even more scarcity, so people will keep playing for longer period of times chasing items. Again damaging the experience of many players that don't become addicted by the (imaginary) loot hunt (addiction feelings are not the same as enjoyment product of fun gameplay, which is way more preferable; many people can sink 1000's of hours into a game because of raw genuine fun, but not many can do the same just because 'grinding').
The game economy it's limited by it's own design (gameplay, lack of proper consumption, etc), and you can't revolve your game around trading without a proper economy (which this game, totally lacks). Unless you can design a proper economy (good luck with that, as implementing proper consumption in a pve driven game has it's own share of problems), in an ARPG trading should always stay secondary (and that's the route most ARPG's and/or modern themepark pve MMO's are following for a good reason).