Commitment just as often encourages treating the relationship as a sealed deal and thus putting much more effort into its maintenance. If you're being rational about it being in a failed marriage is a miserable experience that nobody enjoys living, so it makes more sense to put in effort to avoid that situation. If you're in a failed long-term relationship with an easy escape hatch you might not put in effort to fix things before they get really bad, because worst case you can just leave. In both cases if you aren't willing to put in work to fix the relationship there won't be any fixing it, so if you think you're that kind of person then yeah I would say you should avoid long term commitments to other people, marriage or no.

Not in my experience.