Hi @Robert_Rohm ,
Yeah I am also having bit trouble with the fun factor in this game.
BF4 was the last game in this franchise I had real fun with.
So while I find the contemporary era and weapons much much more fun than previous boring history lessons we got in BF1 and BFV, then the fun factor is simply just not really there. Due to the so many things missing or broken of what makes a Battlefield game a Battlefield game...!
Regarding the unlock of weapon accessories, then they are all linked to how many kills that you get with each weapon. So while your XP ranking up to 100 will unlock all weapons, gadgets and vehicles in the game then each weapon will only unlock all its accessories as you progress with accumulating kills with it. Think we need approx 30 kills with most weapons to unlock next accessory for it. So for many weapons you will need many hundreds of kills to unlock them all.
Also please note that EA have put a cap on XP/weapon credits that you can earn per day in the Portal and singleplayer/co-op areas in the game, so the weapon accessories unlock only really works in the BF2042 core areas of Conquest and Breakthrough. Any kills that you get in the other areas of the game do not count towards this until further... (EA disabled it after a few days due to some players abusing boosting to gain the unlocks)...