The laws of physics are one thing - opposites certainly attract in the world of magnetism - but the laws of romance are somewhat more complex and variable, I suspect. It has been my observation, and based on nothing more scientific than that, that where a relationship between extreme opposites endures it is invariably because one of the participants is unusually tolerant or adaptable, able to accept and 'reshape' to fit their partner.
Some might suggest that a D/s relationship is of this type, but I would not agree. A Dominant is not inherently self-centred, quite the opposite as s/he must be attuned to the needs and responses of their submissive and put those first. The sort of relationship I have in mind is one where one partner tends to shine, enjoys public success, a high-profile career, perhaps, and this may only be possible if they are shored up by a quiet, dependable 'rock' to absorb the more mundane realities of life.
Can such relationships stand the test of time? Yes, and many do. Are they healthy and fulfilling relationships? Who am I to say? All I know is that I would not fancy being at either end of one myself..
That is not to say that differences are not to be welcomed and celebrated. Variety is the spice of life, and all that. I know many, many couples of mixed race who rub along together without any obvious problems, at least none caused by their ethnicity. To a lesser extent, but still perfectly possible, are couples with different religious beliefs. I tend to think that those who adopt sharply differentiated political colours have the most trouble tolerating each other, perhaps because they may have equally disparate values.
In the world of erotic romance which I inhabit, characters are frequently drawn to the unknown, the exotic, the mysterious, the alien. It is a common trope in romance and erotic fiction, and our bookshelves groan under the hordes of millionaires, masters and slaves, other-worldly alien alphas, dukes and commoners, Arab sheikhs and pale English roses. We are asked to believe that these liaisons could work in the long term and maybe we accept it because after all, it's a nice idea. If this can work, if there really can be a HEA from such inauspicious beginnings, then there is hope for all of us.
In real life the situation is more prosaic. Shared interests and common values are the bedrock of most long-term relationships. Couples who understand each other's view of the world and better still, share it, have less to fall out over.
Opposites may attract superficially. Any of us could get carried away on a heady wave of adventurous lust, passion made all the more spicy by that hint of the unknown. Such explosive fervour will be intoxicating while it lasts, a frenzied firework of excitement which bursts into life but just as quickly fades and fizzles to leave a burnt out shell. A true HEA is more like a candle, steady, stalwart, eternal, and for this we need to at least have a common language to express it.