It's random lootbox.
Not good for the integrity of the game (makes it about luck, not effort, skill etc).
Clearly you can get dupes, which means all the time, effort (and in a lot of cases, directly money) is wasted. One person will get lucky and get no dupes, another might have to collect 3 or 4 times more chests to get the same set. Not fair or reasonable. Just luck and bad luck.
It goes way beyond just dupes though.
Some of the gear is utterly useless by design. A defence ring that has a set bonus that increases offence % for bestiary is UTTERLY useless.
Other pieces of gear become useless because they are randomly rolled to have the weakest starting stats. Given it takes hundreds of thousands of mooncoins to upgrade gear now, rationally you have to just ignore this gear
If you got your mooncoines back when you sold upgraded gear then the equation would change significantly. You could upgrade weak gear and then just switch the investment into better gear as and when you got it.
But the nothing back system basically means that ALL gear is useless and the only way to rationally approach the gear is to ignore it all until you get a near perfect piece that you want (of course you can lose patience but eventually you will always regret the waste of mooncoins).
Ultimately the whole system is about money not about making a quality, meaningful game. Not suprising therefore that the players hate it. It doesn;t make sense, because making sense isn't the point.