The potential player loss due to inventory restrictions is negligible because you're mentioning problems that every MMO has. They all have storage limitations. They all require you to manually discard or sell off items you don't want. WoW even has useless vendor trash drops off mobs with the sole purpose of cluttering up your inventory or wasting your time if you're willing to check each loot drop one by one to see if it's an item you want to keep.

Quite honestly, this game is very generous in the amount of default storage each character gets for no effort other than advancing through the MSQ far enough. 140 on the character, another 350 once retainers are unlocked and another 70 once you get your chocobo for a total of 560. That's not even including the Armoury chest and glamour dresser reserved for gear.

It's not an issue for the majority of players. The players primarily affected are the omni-crafters and they have problems with storage in all MMOs.

Quit if you're not enjoying the game but you're kidding yourself if you think you can walk into another MMO and not have problems with storage, especially if you intend to be an omni-crafter.