Call me old fashion. Two people marry because they love each other. They do not need to swap etc.
Again, it has nothing to do with being old fashion. Swinging has existed since the dawn of man.
There are many couples and marriages out there that don't swing who don't love each other.
There are couples who have done swinging where it has caused the relationship to breakdown & fail, there are couples whose swinging have enhanced their sex life resulting in a saved marriage or relationship, and there are couples who swing for no particular purpose because it's no big deal to them & they enjoy it.
All these instances exist, so we shouldn't & really cannot pass judgement. And because of this, the "one size fits all" opinion is not a valid one. But you are certainly entitled to it.