Ion cubes are not pathetic, I had some fun doing math for this. But here goes.
Let's play by the rules of the game and the PDA, and take the data entries to heart.
New York uses roughly 51 Terawatts(hour) each year. (quora + NY times).
51 Terawatt(hours) is roughly 43,881.5 kilotons of TNT.
Each Ion cube can output 5 kilotons.
Meaning the entirety of New York's power annual power needs can be met with 8,777.3 ion cubes per year.
We have access to the antechamber, powered by geothermal energy.
The antechamber has a pillar that creates an Ion Cube Cluster in 2 minutes. Drilling this cluster gives you 3 ion cubes, and takes about 15 seconds.
So let's be generous and say it takes 2 minutes and 30 seconds to get 3 ion cubes. In 1 hour, a prawn suit worker can obtain 24 ion cubes.
Let's be even more generous and say that these prawn suit workers are only working 8 hours a day. In one day, that's 192 ion cubes if they are working an 8 hour shift.
In one year: 70,080 ion cubes.
In 46 days of work (1 month and a half), enough ion cubes have been obtained to meet all of New York's power needs for a full year.
You were right about a few things, but missed the bigger picture:
The ion cube isn't the sharpest knife on the block in terms of power output. However, with the antechamber facility available, (assuming that maintenance is upkept and available), it is the best power source simply because of availability, and accessibility.
Unless the world went full fallout world with cars that go nuclear every time it gets in an accident, there's not many practical applications of U-235 in something that isn't a nuclear reactor of some kind. You don't just slide it into a battery slot and turn a computer on. Ion cubes can be used in more ways than reactor fuel. And EVEN IF, we had that kind of technology for mainstream applications of U-235. There's the problem and costs of refining and obtaining it.
Only 0.7% of uranium ore is U-235. You'd have to go mining into deposits and veins into the Earth's crust to get ore, just to lose a majority of what is mined in order to get that 0.7% U-235. Keep in mind, after mined, this U-235 that exists in natural uranium ore isnt enough concentration for nuclear fuel. So you have to enrich it. And the processes go on and on.
Meanwhile, Hibbly Jim in a prawn suit can get me a nice green power cube every 2 minutes and thirty seconds. As a matter of fact, and I quote, the ion cube fabricator data entry says this:
"This device appears to be the origin of the raw mineral that forms the base of the ion cubes which power smaller alien systems. Likely drawing power itself from the main thermal plant, this device may represent an almost limitless source of energy." This is created artificially, grown artificially as the ion cube data bank states.
Ion cubes come from a machine that can create them every 2 minutes, meanwhile U-235 has to go through tedious and expensive processes to not only to find a vein and mine it, but get it into a form usable for nuclear fuel. (btw, just getting the U-235 out of the ore takes more than 2 minutes, if that wasn't already obvious.) Getting U-235 in a usable form is tedious and finite. Ion cubes are not.
When you look at it like that, Are Ion cubes so pathetic after all?
They aren't the sharpest knife on the block. Unlike the others though, this one doesn't dull.