The latter doesn't sound reasonable, no. To "preserve established traditions or institutions"

Well, to me there must be a very good reason to preserve established traditions or institutions. "Because my father's father's father always did this/believed this way" isn't a justification to "preserve" traditions, particularly those I find abhorrently inhuman.

To "resist or oppose changes in these" again--it is only the reactionary who resists and opposes change because they wish to remain "moderate, cautious, safe" IMO. To resist and oppose change, which is inevitable anyway, has never made any sense to me whatsoever. Especially since there is precious little any of us can do to prevent change from coming, regardless of our political persuasion.

So no, I don't agree that conservative sounds "mostly OK" at all. I think it sounds much more like a river in Egypt, as they say.