Yes, "long" in Church parlance means "centuries," and that highlights one of the problems of a statement like this: the concept of "homosexuality" as an innate and fairly stable personality trait, and of "gay" as a lifestyle, a community, and a political/social lobby, are of very, very recent origin.
The word (and concept) of "homosexual" as a distinct personality type wasn't invented until 1869, when it appeared in a pamphlet written by Karl-Maria Kertbeny protesting Prussia's anti-sodomy laws. The word "gay" (meaning something other than "carefree") didn't come into vogue until exactlly 100 years later, when you had a defiant, politicized "gay movement."
Thus, until very recently, you really only had two concepts: "sodomite" (a man who had sexual intercourse with men) and -- well, there wasn't a word for it, but you might say "struggler" --- a person who struggled with temptation.
And by the way, "struggler" would not be specific: it could be one who struggled with homosexuality, or the more typical kinds of lust, or alcoholism, or any other moral difficulty. It includes about everybody: even Jesus was "tempted in every way that we are" and is even said to have "suffered" from it (See 2 Corinthians 1:3-5.)
I guess it could be argued that since we're all strugglers, then men who struggle with homosexual tendencies shouldn't be excluded from consideration as potential priests, any more than any other man who struggles with "commonplace" lust, or alcohol (the Venerable Charles de Foucauld comes to mind on both counts) or any other besetting weakness.
On the other hand, the priesthood is a confraternity of men who often live together in close circumstances: in the seminary, for sure; in the monastery if they are in religious orders; and even in the rectory, where priests may live together in 2's or 3's or more, for years on end. This would present a life-long exposure to temptation, and thus (severe) suffering and (severe) moral risk, for a man who experienced acute emotional and sexual urges toward other men.
In all justice, you don't put a same-sex oriented man in a seminary, or an alcoholic in a brewery, or a carb-addict (like me) in a retail Krispy Kreme.
Not if you love him, REALLY love him, and care for his soul's salvation.
Now the question is, how DOES such a struggling person avoid temptation? In the old days, the "vocational" choices were pretty much confined to "Matrimony or Monastery." But if a same-sex-attracted man wants to live chastely and avoid temptation, what's he gonna do? Should he marry a woman, if he's capable of intercourse with her? (Doesn't seem like a recipe for marital success.) "Monastery" seems to be out, as well.
Hermit? Some have done this. But not eveybody is psychologically cut out to be a hermit. So, what life of reasonable human happiness --- including the friendship and human sollidarity that everyone needs --- is to recommended for our chaste strugglers?
Real question here, looking for real answers.
It is a good question. One point that comes to mind for me is that there have always been people, heterosexual men and women, who did not have the opportunity to marry, as a practical matter, for a variety of reasons. They have no choice but to be celibate, whether they like it or not.
The same is true for those who are attracted to the same sex.
"And by the way, "struggler" would not be specific: it could be one who struggled with homosexuality, or the more typical kinds of lust"
What's missing from your equation is that sexual desire for the same sex is not a natural component of the human being as is sexual desire for the opposite sex.
It is a symptom of a mental disorder, and the first best chance of a sufferer to find happiness is to get into treatment.