The gun is bad but its not as bad as you are describing, how is a Churchill NA playable to you with a turret far inferior to the Comet, and a gun that does more damage but is far less versatile? A Comet at 4.0 would be a slaughter. I usually despise Gaijins harsh BRs for Britain but I can only see a comet as low as 4.7.
Im also not aware of many if any 2.7s that can “lolpen” (which implies not having to aim) at a turret that is a minimum of 100mm but more importantly half of the structure is layered with another 100mm aswell as a bunch of sloped and jagged edges everywhere. Even with a Panzer 4 F2 (I believe that these Panzer 4s are undertiered personally because germany players are noobs) the best most reliable shot would be the very edges of the turret as the center can run you into a 200mm black hole.
When the APDS had good pen the Comet was a very strong hull down sniper, able to penetrate sloped armor well, bounce shots to the turret and also great optics to boot. It still has some advantages in its state that would make it an evil vehicle at 4.0, I mean, how is the American 75 going to pen your turret reliably, or the Soviet unless they all aim for the cupola.