This game is a trading simulator not a gear grinder

There is no real point collecting gear for endgame (or any part of the game for that matter). You should only be trading for gear and I don't really get that.
I have tried many times to upgrade items and its really just a waste of time and resources. Finding good gear is pretty much impossible (ie by looting).
the trading website is indispensable.
Maybe there is an OP mechanic to get +6 to melee skills and high dps that I am not aware of...maybe everyone else is just luckier than me or maybe not many people buy the gear on the trading website...idk....
I think it would make more sense to do a crafting system. Maybe you need to grind materials to upgrade things to what you want them to be.
if you are going to leave it as is, bosses need to be consistently dropping good gear on the class that you are on (or enough mats to buy things eg divs). corrupted items that drop need to be with all slots (not just four) and be at full quality. in fact get rid of gear drops not on the class you are on and other weapon types / stat splits that you dont want (maybe a player can select the types of drops (staff/wand/etc and even the bases to drop).
by the time that you are level 70 only expert gear should be dropping and the perk pool should skew better.

You don’t like the slot machines? Come on, even toddlers can figure that one out. Maybe you prefer the kiddie rides—you know, the ones that make those cute smiley faces? 🧸

Oh, you're in it for the participation medal? Sorry, my friend, but in this game, we farm loot like it’s our only purpose in life. Forget that 9-to-5 job; just 10,000,000,000 hours in-game for one legendary drop. And when you finally get it—thank us. 🙌

Praise the RNG gods and prepare to waste all your precious time and patience, chasing that elusive jackpot. 🕵️‍♂️

All hail RNG! Don’t worry, no fun police here; we’re all about that RNG grind. 🎲 RNG all day, every day!

All hail RNG! 🎉

No, there will be no other source of good items beside the market. If there are such a sources the game will be completely different.

I believe that.

And I know it's probably rude to give a link to your own topics, but maybe this will answer your questions

When there are fewer players, the market will be scarce with fewer items to buy. So that would dry out too when player base drops.

The only reason why trade is the place to get the better items is cause when say 100k players are dropping lets say a belt at the same time. Out of that 100k, 1000 of them would be good enough belts. Some will use that to upgrade and others will put it up to trade and possibly a decent belt from the one they swap out to then trade.

A single player is not dropping 100k belts. and it would take an extremely long time. crafting kind of just speeds that up a little to get something of your own if possible. In POE 1 it is much much faster to re-roll in crafting to significantly speed up for an epic upgrade.

GGG is well aware of the low drop chance to get great items for a single player. And i believe they've set it like that so that trade is effective. But nobody wants to admit that its what they been doing for a very long time.