-How's the bots,hackers and spammers issue going on?
Greatly reduced and its much less of it now, you may have 2-3 spammers that you need to block during the day but thats it. Bots only saw like 3 in the past 2-3 months.
-Have the servers been improved? (latency)
The question is rather broad. Some people blame the servers while when you do an actual check its the connection route from their ISP to the server which causes spikes. If you have a lot of these try sending it to support, they will check it with you and perhaps solve it even, they did it for several players.
-Have they optimized the game in any way? (fps drops)
Fps still drops if you have a lot of people around. But i actually think its better than it was, but depends per player and system.
-Is getting geared up/upgrading still so demanding to play the game as your full-time job?
Arent all other MMO's this way? Every MMO has a grind to it some more some less. Considering prices for a lot of materials dropped to the floor and some have even more ways to be obtained now, and adding the cost reduction they will implement in the next 2 days i say its easier to upgrade than what it was before. Not to mention with the current oceanic event you can get nebula stones which already reduce costs to upgrade accessories when used.
-How's the game's population going on? Is it bigger or not, than ... let's say 3 months ago? + or -?
Its smaller but still a lot of people play the game, i would say people come and go, just cause you dont see them around doesnt mean they do not play.
-Are the disconnects still there?
Never had any from my side which are game related. Had only 2-3 dc's but thats cause of my WTFast which lost connection to their servers and not the game itself.
Someplayers randomly DC during porting,
All in all, if you have nothing better to play just come back, play again for a while and see if you find it different. I think its worth to come back to tho.