The system Cryptic has used at least since I've seen S7 launched is a 'equal available for all' stance on gear. Can you get sets from random world or instance bosses? AT random? Meaning it doesn't matter how many times you do it there is NO guarantee you will receive it? No, they implement 'reputation systems' which gives it to everyone after criteria are met which works for SOME things in an MMO but not all your end game gear...even with 'timers' on all your 'projects', there is a predictable and obvious end to the quest to get it, with no random chance involved at all. This does not work.
This is why IMO the STF system in itself was good, though tweaking was needed with the way it was laid out. As much as many people complain that it was 'impossible' to obtain all the pieces for a full set because of the RNG, it still required players to engage in the missions and instances and at least you knew every few times you did it you would be able to exchange your EDC(? I cant even remember now) for a piece of Borg Technology whether you got your 'drop' in the STF or not. So yes, people get mad they don't get that piece for their set but at least they weren't bored and finished with the content in a matter of weeks.
I'm not sure why Cryptic hasn't gone to the PvP area, it's MUCH easier to create/add PvP content than PvE content, that's a given. They could have improved the PvP area a lot, then given players reason to delve into that area again for awhile until they could get some more PvE content created. Rinse, repeat if necessary....it's kind of the life cycle the game needs to go through. STO just seems to be stuck in one direction without new 'Season's' bringing the necessary environmental changes.