..one reason is because the show was promoted as if the tech was going to undergo a significant development.
And then it underwent exactly that: Earth spaceflight transitioned from pre-phaser to phaser era, making deep space exploration survivable for the first time. So what's there to complain?
The show didn't reveal to us how it was before Kirk-style adventures became possible (except for the pilot episode). It revealed to us how Kirk-style adventures became possible - apparently through the adoption of phasers, photon torpedoes and modern warp drives. A sound dramatic concept IMHO, and in keeping with what was promised (although I'd consider such promises irrelevant in general, as they are completely external to the fictional Star Trek universe that is my main interest here).
I think Worf has stated on screen that there were no phasers in the 22nd century in the TNG episode guest starring Matt Frewer.
The exact question Worf was answering (even though it wasn't addressed to him, but to Riker) was "What do you see as the most important example of progress over the last two hundred years?". It would be valid for Worf to answer "Phasers, because they were developed during the past two centuries: they didn't even exist yet when the 22nd century began".
Really, Riker's babbling about the warp coil being a post-2150s invention is the more worrisome thing about that episode ("A Matter of Time")...
And as pointed out above, it appears that lasers were the Starfleet system in this role in "The Cage"
Possibly. However, phasers were also available in that era, as "Obsession" establishes: they were the weapon system that Kirk hesitated in operating, back when the
Farragut was attacked by the dikironium cloud. Lasers could have been limited to sidearm role only - or they could have been an "extra blade" in the Swiss Army sidearm of the day, parallel to the phaser "blade".
..and reference to "atomic" weapons for the Romulan War a century earlier was made in "Balance of Terror."
More specifically, to "primitive" atomic weapons - as if Kirk and Spock were flying a ship armed with advanced atomics. But granted, the choice of giving Archer something that appeared non-primitive in relation to Kirk's stuff and then establishing that Archer's adventures preceded the Romulan Wars was in spiritual contradiction with this TOS episode.
...they were in no way required to give the earlier tech almost identical names or make the VFX for it virtually identical to what had been seen in the past.
I really don't get this part of the argument. What possible point would there be in giving a misleading name or appearance to what clearly
is a phaser? If the point was to show that this is how Kirk-style adventures were made possible, then the connection between Archer's phasers and Kirk's should be as blatant as they could make it.
The show could have taken a different dramatic tack, yes. But on the tack it took - of directly associating Earth's first deep space forays with the introduction of "Kirk tech" - did not require and really did not allow for misleading terminology or visuals.
or perhaps actually caring about and documenting the location and function of the plasma cannons that appeared in the pilot (did they ever appear, or even get mentioned, again?)...
I don't think we can count that against ENT. They were pretty clever about it: they gave the ship 13 visually distinguishable weapons ports, and the writers and VFX wizards were then told they could place whatever they wanted behind those ports. The writers/VFXers apparently used two topside ports for the original plasma cannon, and never reused them for anything else, so that angle is covered. They did mistake the "turbocharger caps" on top of the hull booms for additional weapons ports, but then again, the caps were never established to be anything else, either. They did look like somewhat larger gunports...
Timo Saloniemi