I think the suggestion that clickiness leads to acceptance of all ideas is flawed. On a practical level, people who click on a number of topics tend to hold few or no inaccurate beliefs (bolstering the unconquered-territory theory), but significantly, they also tend to only adopt good beliefs. Some ideas click, while others which seem to be just as subject to first-blush judgement (eg. “People should only live out their natural lifespan.”) are rejected near-instantly.
On the metaphorical level, I think the game example holds up as long as we assume that the territories we are discussing are desirable—that is to say, everything we are looking to conquer is good, and some parts are easier to get than others. Those regions which are bad (eg. full of monsters, corresponding to some irrational belief like homeopathy) are discarded even before the “preclaimed/free” evaluation is made. Given that, it seems to me that only some things click, but we’ve already divided the space of possible ideas to remove those which should be avoided altogether. Here however, the capture-model seems to fall down a bit—while sometimes we see that an idea is probably good but hard to hold, and then painstakingly reason our way there, there are some places which are incorrectly declared downright undesirable.
In addition to the very valid counterpoints listed here, I think its worth noting the false dichotomy of the question. If the initial assumption is that population is capped, that hasn’t been borne out yet, and assuming we eventually leave Earth in a sustainable-habitats manner, doesn’t have to ever hold true. If population-capping isn’t the basis for your statement, then I don’t see anything suggesting that the total number of people will be the same with and without cryonics.
We are not choosing between ourselves and future potential people—at the moment, we are simply choosing between possible-ourselves and definitely-not-ourselves existing in the future.