Au contraire, taking rights as if they're defined absolutely means that conflicts between them cannot be resolved equitably, but rather only binary-axiomatically. In this US, this plays out as most natural rights being undermined through inescapable interactions with corpos, with the justification that you've "voluntarily" agreed that you will not exercise your right. There are some exceptions of course (eg Pruneyard v. Robins), but they're more like exceptions that prove the rule.
US courts giving insane leeway to corporations in what a contract can include has nothing to do with whether rights are defined absolutely or not. The exact same scenario could play out if the voluntarily waived rights were reasonably limited rather than unlimited.