Okay I'll break down Zombs roles for you, the common situation where he frags and where he gets killed.
CT Anchor: He uses his utility to delay the push and buy time for the rotation. He often anchors directly on-site. Often enough, when the enemies are in, he'll have to stay alive as long as possible before at least 2 people swing and kill him. He usually gets at least a frag. When the enemy team found another player on the site that is not him, he also gets the trade and makes sure that isn't a free kill.
CT Retake & T Exec: He doesn't push first. His putting down the smoke/wall/suck will signal the start of the push where his teammates rush in and get the majority of the kills. He'll be a little late and will enter to clean up. I cannot count how many time his walls has completely ruined the enemy's post-plant or push.
On Sentinels, Tenz, Shahzam and Sicks are usually the main fraggers. Even Shahzam bottom frags a lot of times playing Sova, doesn't change that his Sova plays make or break the map. Dapr gets a lot of kills because he is the lurker, flanker on Sentinels. On CT Haven C or CT Ascent A, Dapr got saved and got so many kills just from Zombs' putting down the fattest paranoia or astra suck at chokepoints.
I do agree with you that at a player in an FPS gotta frag, that was why shinobi was dropped from C9B way back when. But zombs is nowhere near that point. If you like stat so much, for the past month, zombs averages at over .9 K/D, a little better than say Vanity (the reason why V1 is tier 1 in the first place), and close to Ethan's K/D when he plays smoke.
Now I know that this is an online forum and people are here to prove themselves right and not to find themselves opening to other opinions. However, I do hope that when people do reply to you with no ill intention, you return them with the same amount of respect and politeness.