Things that need Improvement

After 300 hours, I rand into some aspects of the game that in my opinion need massive improvements and this is what I'd suggest:

Suggestion 1: Trade NPC
Add an actual trade npc, just like the currency exchange, but for Items.
Why?
I am 100% not the only one fed up with trying to buy something and pinging 20, 40, 100 people, just to not receive and answer. A regular trade npc would solve the "no response" problem for the casual player and at the same time, it also solves the pricefixing issue, because once you place your high end item for 1 exalt, it won't last for ever in the search history.

Suggestion 2: Trainingsdummy/Boss Gauntlet
This is something I've seen in other games and fell in love with and I think in a minmax heavy game like POE, a trainingsdummy or a boss replay area, where you can fight already defeated bosses (without any rewards or penalties), it would greatly enhance the experience for people. The build crafter can go all in and minmax their builds,while casuals can practice builds on something that won't die in a fraction of that you aim to hit for.
A good example would be the build that I'm going for, it requires some time to setup, which is if done correct hits like a truck, but getting that setup right needs some practice. I can't get this practice in, because The only bosses that won't die with a fraction of the setup are map bosses, but on those I get only 1 try to of practice and once it went right or wrong, I'll need to clear multiple maps without bosses, before I get an other try.
This makes it really hard to learn from because not every mistake is obvious.
an even better solution would be a boss replay, where I could practice my skills against specific bosses, rather than a stationary target.

Suggestion 3: Mapping
The endgame feels right now absolutely underwhelming and not even close to how it was presented in the trailer. Mapping in general feels boring, since you do the same stuff over and over and over again, without any sense of direction.
For maps in general, I think a better solution could be a lite version of the specific mechanics, where do run the map as if it is the pinnacle boss map, minus the pinnacle boss (maybe some boss as replacement). For example where you'd run a breach map like a timed dungeon and a chest at the end, rather breach just sit in a random map and be a farm fest for 3 minutes. Or a delirium map being something like the escape rial from Sekhemas Trial.
If that map fails, then you go back to a regular mapping node, where you kill all rares.
Edit: An even better idea would be the map mechanic being the requirement to finish the map. Once you've reached the reward chest, the map counts as finished, but you still have the option for the boss, which will disappear on fail, but at least the map is not completely wasted.

Suggestion 4: Citadels
This one will be short, add some ping that indicates "Warmer/colder" depending on the distance of a tower to a citadel. This entire mechanic tilts me and, by the looks of it, many youtubers, because there are people that find 20 citadels in a day and other people spend hundreds of hours without reaching even one, just collect all items for the actual big encounter, where you get only 1 try and if that fails, well, good luck for the coming 300 hours of mapping.

Suggestion 5: Atlas Search Option
An other big oversight in my opinion is the lack of a search option on the atlas. A menu, where I can select "Boss, Corruption, an other map option" is a must have for an ever expanding map

EDIT2:
Suggestion 6: Monsterhitboxes
Please make monsters stop pushing other monters around, which then will push me all over the place. This is probably THE most frustrating way to die, simply because in a high density encounter like a breach, some random cracked monster runs into an other monster, which for some reason is now able to push my character and oftentimes they push me into some big aoe, away from my aoe that would clear the enemies around me and give me some breathing room or they push me entirely into a situation where i get completely overwhelmed.

I think those points would be my biggest issues with the game so far.