Chance (or, rather, a combination of unknown, unforeseen factors) plays a part in love, just as it does in evolution and horticulture and everything else.
Certainly, there is plenty of information on which we can base a 70+% accurate prediction of whether an individual will find someone to love; whether they will stay with one partner for a long or short period; whether they will be happy and successful in a love-match.
When you put all the eligible people on Bell curves for each of about two dozen mating factors, you'll probably find the same distribution as with most other kinds of human endeavour. The 60% who fall within normal range in all the traits have the best chance of finding multiple potential partners in the general population. They may have to make some effort, but not work very hard, to meet compatible others and and keep the relationships they want. A great deal can still go wrong, both through their own bad judgment or bad management and through circumstances beyond their control. How they cope with things going wrong is a measure of the depth of their commitment.
The farther a person falls at either end of the spectrum in more characteristics, the fewer compatible other people there are, and so it becomes harder and harder to find one. Very close to the fringes, their odds may approach zero.
Still, even very unusual people can improve their chances with strategy and perseverance.
And - you're quite right: maybe not everybody needs or wants to be involved in a love-relationship. There are other ways to live well and be happy.
The only thing people defend more fiercely than their illusion is their denial.