Aside from the stated reason for the side-quest removal, it's far more likely it had to do with $$$$$ than anything else. Simple put, people running greatly outdated content are not swiping their plastic. And the faster they get to higher levels the faster they are likely to. BnS NA/EU revenue was down in q1 https://massivelyop.com/wp-content/uploads/2018/05/ncsoft1.jpg and it doesn't take an economics degree to follow what's probably going to happen to address it. Minimize, economize, nothing to see here quickly on your way Cricket.
As for the weapon, the Hongmoon one was nice but it's big brother, the Baleful/Seraph weapon took it's place. You still have to evolve it just like you had to the Hongmoon one. And frankly, the old weapon was the epitome of grinding and rng. We get enough of that at endgame. And again the previous reason comes into play regarding people stuck in outdated content grinding for upgrade mats when they could be at a much higher level swiping for endgame mats.