ASIDE: Your point is mute [look up "moot" before attempting correction. 8-) ]. Enough is enough, and any less is not enough. That's the definition of enough.
Consider: "If you eat enough pudding you'll die"... the only test case is to keep eating pudding till you die. If you stop before you die you didn't eat enough. 8-)
Now the point that all eyeballs are not equal is fine and obvious. It only takes one metaphorical eyeball, connected to the correct brain, to find a bug. So one is enough if the rest of the configuration is suitable, and an infinite number are not enough if they lack the context.
The real difference between FOSS and others is not the quality of the eyeballs but the opportunity for the correctly quipped eyeball to fall on the relevant bit. In closed source applications the right post-eyeball configuration would have to first be part of the set of allowed eyeballs, and it would likely have to be actively paid to look for the bug directly or indirectly since the limited herd of eyeballs all have their assignments.
Pretending that the better solution (FOSS IMHO) is unworkable because it's demonstrably imperfect ignores the fact that the far less functional (NON FOSS IMHO) has a demonstrably worse track record. That comparason and derision is just "false dichotomy" and kind of an example of, perhaps, why you aren't the set of eyeballs in charge.
In non-FOSS circumstances virtually all eyeballs lack the context to find and fix problems because they lack access to the source.
So your argument fails because it implicitly argues against exposure, or argues that exposure isn't enough if the right people aren't looking. The failure isn't one of fact but of position. You offer no counter proposal. You are pissing on the model that exists but offering no alternative. In short you are engaged in venting of some sort but you are apparently not one of the set of eyeballs ready to offer solutions.