Most of your cons are saying swords are better, if that's so then maybe you just prefer swords.
I don't use AP as a main weapon when being gunner, it's better as a side weapon when primarily using swords.

no knockback is good. it lets you assist others without knocking them out of their way.
in fsc I use it to shoot zombies when there's spikes in the way and not enough time to use blitz.
or sometimes I use it to keep up the attack when I back off due to their attacking.

click click is annoying but I use a gamepad so i don't worry about that.
Also, it's my favorite weapon to break boxes with at the end of danger missions.

Kesari, the charge shots ricochet in both directions. If the regular shots ricocheted in both directions, then the alchemers would be overpowered. If the direction of ricochet were random --- sometimes left, sometimes right --- then they would be underpowered.

The ricochets are crucial to the alchemers' design. In the hands of an unskilled player, alchemers do poor damage (lower than other guns). In the hands of an expert, they do close to twice as much as "poor" (higher than other guns). I for one really like this aspect of the game's design. Newbies can survive, but experts can take pleasure in honing their skill.

>>Never use Polaris that's for newbies.
If there's a finer firearm for Walker hordes, I've yet to see it in the two-and-a-bit years I've been playing. The Polaris gets a lot of flak for being visually distracting, and for the knockback being rather disruptive in team play, but that's a matter of deployment; a skilled wielder who's minding their surroundings can do horrendous damage without treading on anyone's toes.

The Argent Peacemaker, indeed the Antigua line in general, make great support weapons, but they don't really have the stopping power to be arsenal linchpins. Their strengths are kiting and hassling, mostly; the lack of knockback can actually be an advantage in teamplay, because you can contribute chip damage to enemies who're engaging teammates at melee range without risk of throwing off their attacks (i.e. the principle reason the Polaris draws so much ire). But yeah, used as a primary weapon, you're going to spend a LOT of time watching shells ping harmlessly off advancing monsters, punctuated by panicked reloading. Alchemers are generally better weapons against Mecha Knights and their thrice-cussed automatic shields, because you can use the ricochet to tag them from the back. The long cooldown on said shields means that it's possible to get a few cheeky shots in with an AP if you're careful with your timing, but again, you're unlikely to be doing a lot of damage in that window.

Jenova is exactly right about their utilty vs Spookats, too; the high projectile velocity and ROF coupled with their superb mobility when compared to other EL guns makes them excellent sidearms for Undead strata, though I'd couple it with a sword or a higher-damage gun.

(I have a gunner loadout for Construct/Gremlin levels that uses both Antigua guns, but it's basically there because so I can feel like a space cowboy rather than because it's particularly useful.)