I don't know what you mean about immediate power. Pre transformation A-Gren's specs hydro pump hits significantly harder than Koko's thunderbolt, and all of koko's other moves are piss weak. Moreover, the speed is only relevant to a couple of mons that are mostly not relevant to the meta (Weavile) as well as Koko itself.
Besides that, they're not really comparable. Koko's an offensive pivot. A-Gren is a breaker/cleaner.
I also don't know about these A+ mons being dead weight. Lele, Mawile, and A-Gren heavily pressure the other team by their mere presence, because nothing besides like Megagross wants to take hits from Lele's psychic, nothing wants to come in on Mawile's attacks, and no one wants Gren to transform. Celesteela is an excellent and consistent wall on one set and a similarly excellent and consistent sweeper on the other. Unless it's a team of something like all electric and fire type moves, it's not going to be hit or miss.
Ash Greninja's Specs Hydro Pump pre-transformation does not hit significantly harder than Koko's Thunderbolt
252 SpA Choice Specs Greninja Hydro Pump vs. 4 HP / 252 SpD Eviolite Chansey: 118-139 (18.3 - 21.6%) -- possible 5HKO
252 SpA Magnet Tapu Koko Thunderbolt vs. 4 HP / 252 SpD Eviolite Chansey in Electric Terrain: 109-130 (16.9 - 20.2%) -- possible 5HKO
252 SpA Life Orb Tapu Koko Thunderbolt vs. 4 HP / 252 SpD Eviolite Chansey in Electric Terrain: 121-142 (18.8 - 22.1%) -- possible 5HKO
As you can see, LO thunderbolt damage eclipses the specs hydro pump damage.
Forget about gross damage for a minute though. Koko's actual damage output dwarfs that of pre-transformation Ash Greninja. The fact that Hydro Pump is only 80% accuracy means that Thundbolt has roughly 125%+ the damage output in comparison. Then there is the fact that Koko has access to Nature's Madness, which will take 50% off of literally any switch in bar Shedinja. The combination of the two moves alone is incredible in terms of damage output and is something Specs Greninja cannot match. On top of those you still have to account for the fact that Koko can actually use different moves without being locked in while maintaining the superior damage output.
The speed is highly relevant because
it is the fastest non mega in the tier. It's faster than dangerous threats like Greninja, Torandus, Weavile, and Dugtrio.
I only compared Ash Greninja to Koko because someone else did. The point that I was making is that "often forced to come in and u-turn while accomplishing very little considering" applies to Ash Greninja as well, if not more so due to the amount of things that can stop it cold like AV tangrowth, Chansey, Magearna, Bulu and Fini
I never said the A+ mons were dead weight. I said they have their fare shares of dead plays, which is what was being held against Koko. I think you're exaggerating how good some of the A+ mons are in comparison to Koko. For example, Celesteela needs a lot of support to break past common threats like Zapdos, Heatran, Toxapex, Chansey, Zar Y, Koko. It's defensive set crumbles easily to breakers and lures and is setup fodder for key dangerous threats. I'm not saying it's unworty of being A+, but lets not act like it wont be hit or miss unless the opposing team has all electric or fire types....that's just absurd