Do not confuse evolutionary mechanisms and biological in general.
Biological mechanisms that are stably manifested in a population are either useful, or are the consequences of convergent mutations (which does not negate the first, but may be harmful), or are the consequences of selection support for beneficial mechanisms linked to them.
The homosexuality mentioned in the post also belongs to the latter group. At least some of the genetic alleles that make men predisposed to homosexuality (these alleles are more common in gay men) make female carriers more fertile (more common in mothers with many children). That is, selection supports the increased fertility of women, but homosexuality creeps along with it.
Something like this.
You are confusing the mechanisms of evolution and its results. The mechanisms of evolution are selection, variability, heredity, etc. You are talking about mutations.
Not all mutations (even those fixed by selection) are useful. Moreover, the benefit / harm from a trait is a very situational concept. For example, excess fat deposition is extremely useful in cold conditions, but the climate can change , and then the competition will be won by those for whom this trait has been leveled. In addition, the mutation process is absolutely random. As a result, both a harmful trait and useful or useless ones may appear (however, there are usually more useless and harmful ones) .
There is a debate about "homosexuality" among animals. The truth is unknown, but somewhere nearby.
Harmful from the point of view of whom - a species or an individual? From the point of view of an individual of such mechanisms, a dime a dozen, for example, old animals lose their teeth, and they die of hunger, although they could have lived for some more period of time. From the point of view of the species, this is reasonable, it is necessary to give way (food, territory) to the new generation, but from the point of view of the individual not very much.
Plus, as they wrote here, some changes have both pros and cons. A very striking example is upright posture. Its advantages are obvious, but there is a huge disadvantage - it is much more difficult for us to give birth than in other animals, high mortality of mothers and children, due to the structure of the pelvis. Of course, at the current level of development of medicine, everything is not so bad, but it used to be sad.
I would rephrase the question: "Do all genetic mutations increase the survival rate of an organism?" To such a question, I would answer "no". Genetic mutations are non-directional and random. They can both increase and decrease the survival rate of the organism, as well as be neutral.
There are beneficial ones, there are neutral ones, there are harmful ones, but it is not critical for the population, as already mentioned in the commentary.
There are mutations that both brought benefits and inconveniences, but the benefits turned out to be great.
Concerning non-traditional sexual behavior. First, there is the genetically conditioned, and there is also the socially conditioned - fashion, early learning, violence, etc. Secondly, yes, it is being actively discussed, and what are the benefits of sex. Gender-oriented behavior.
The first thing that occurred to scientists is that such men have daughters even more feminine. After all, this behavior does not exclude childbirth at all. Yes, they may have less pleasure in contact with a woman, or not at all. But "nature" is "not interested" - all the same, some of them breed with women. The ability to feel a woman more subtly gives them success with some women, gives them another facet of artistic creativity, a sensual facet, which again leads to success with women, to commercial success.
He is not so attracted to women that he, everything -so, won't you contact them? Okay, but he will support his relatives financially, they will be in a good position. His sister, a carrier of the same genes as he, will give birth and his genes will be passed on.
Perhaps the mutation provides a benefit that is currently unknown to us. For example, resistance to any disease. After all, one gene affects different functions of the body.
Evolutionary mechanisms do not have any purposefulness, so one can only speak figuratively about their "profitability". Well, it’s probably beneficial for me that my mother once went to study to become a chemist-technologist: because she went on assignment from Gomel to Arkhangelsk and there she married my father; - but my mother definitely did not enter the technical school for my benefit!))
So are evolutionary mechanisms: events just happen. There is in the population a scatter of variants of any trait in a more or less wide range: for example, the length of the beak or variations on the theme of sexuality with a roll left-right, and with extrema, extreme values. And there are vaasche mutations.
Only that which gives a clear loss in the current situation is discarded. By the way, homosexuality is therefore obviously not)) For population survival, it turns out that it is at least neutral.