Because if organic life were allowed to develop and develop it would eventually reach a stage where it could produce synthetics more powerful than the reapers (whih you would imagine would be immune to indoctrination, also I'm not sure indoctrination works on synthetics?). The "solution" prevents that from ever happening and ensures that reapers will always be more powerful than the races, synthetic or organic, they are slaughtering.
While your explanation is sensible, it's based on an implication and not on what the Catalyst actually says. The Catalyst's only stated motivation is to keep the created from rebelling against their creators - in this case, keep synthetics from rebelling against organics, e.g., Geth and Quarians. He supposedly invented the Reapers in order to prevent this conflict, who either destroy or indoctrinate the most advanced species, leaving the weaker/less intelligent species alive for the next cycle. "Without it [the solution]," he says, "synthetics would destroy all organics."
Nowhere does he even allude to the concern that organics would eventually make synthetics strong enough to combat the Reapers. Now, it's a reasonable concern, but the Catalyst seems to believe that synthetics are not a problem. Case in point: Even though the Geth themselves faction into independents and "heretics," the Reapers seem to have no qualm with the Geth - they repurpose them as necessary, but they are not a primary target - hell, not even an acknowledged target. If the Reapers were concerned that synthetics would become more powerful than them, they would deliberately seek them out and destroy them, too.
So really, why should he worry? The Geth are nowhere near as powerful as they need to be to stop the Reapers, and they still broke off from their organic creators. It's implied that organics couldn't even make anything more powerful than the Geth without developing the same problem of cognitive resistance, so why should the Catalyst be concerned that organics could both develop
and control a race of synthetics that could combat the Reapers (since if they're not controlled, what's to stop them from ignoring the organics or joining the Reapers?).
Now, if we assume that the Catalyst is trolling Shepard majorly, and actually orders Reapers to steal organic material for the sake of maintaining his ultimate power, then this line of logic has a sound basis. Unfortunately, though, that's only an interpretation one could make based on the sub-text, which itself is dubious based on the quality of the endings. In short, even our efforts to salvage the ending with logical interpretations are shot in the face by the unbelievably bad execution.
"Someone has an opinion I disagree with, RARRR"
If the reviewer thought it was a 10, he should've given it a 10.
People do have the right to their opinions, yes; but the primary justification for game reviewers is to be as honest and thorough in their assessment as possible in order to help people make informed decisions about the product. At its best, a game review should be a carefully considered argument about the merits and faults of the game in the context in which it is conceived - people might not agree with the argument in the end, but we should at least be able to see the line of logic that led to the conclusion. Thus, if a game reviewer gives the product an excellent score and abstains from acknowledging the many, many logistical and thematic problems initiated by the ending, then that is misleading and consequently, a discredit to the score and the person's reputation.
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