I'll be mean and direct : In a majority of friend zone cases, that troll Onjenae is right. However she/he/it worded it to sting rather than provide a reality check.
I'll provide the reality check.
Yet it remains: often the guy who is crushing on a girl and ends up friend-zoned, has few, if nothing to show that he might be attractive enough to be even a casual hook-up. Quite a few of these are nerds or socially awkward, either scrawny or fat, unkempt, with weird or unpopular side gigs, dressed by their moms with next to no knowledge about male fashion and dressing right, and low assertiveness and high shyness level.
If they would work on these issues and improve themselves physically, like hit the gym, dress nicer, use fitting colors, go out in social clubs and meet out new people with no ulterior motives behind their head than networking, meeting new people, and having fun, and take the energy to invest in themselves not only the pool of girls they'd meet would grow, but they would be actually showing attractive traits like determination, ambition, drive, maturity, growing up, fitness, etc. To get high, you have to start low.
It's sad, because a lot of these guys, if they took the time and effort to work on their appearance, would be much more marketable as potential mates. Girls and women want a guy they can show around as theirs, they want some sort of bragging rights, if only to say "See my guy over here who looks good? He's MY guy. I'm in love with him."
Also, and tangently linked to the above, a lot of crushers that have weaseled themselves into into romantic dead-end zones are crushing on a woman a lot of guys would, in fact, find attractive and who have much more options available to them than their little guy friend pining for her over there. Guys want bragging rights as well, however you don't hear them whine about being friend-zoned by the 200-pounded, bottled-eyes shy girl who hangs up with the girl posse because she's desperate for friends.
Odds are, the crushee is quite attractive, and she's like a buoy to her crushing boy. Hence why they invest A LOT emotionally in this "relationship". A lot of them haven't accepted that first they have to go where they can fit in right now, rather than aiming too high without having the goods to show they deserve that high. But no, the girlfriend has to be cute and attractive. Why aim for little miss plain, shy Jane over there who's never kissed a boy, when you can be friends and have the lottery ticket with Miss Queen Popularity who's so hot and so nice with you. If she's so nice with me, maybe it's because she finds me... cute?
Now if they took the time to work on themselves to improve their attractiveness and their social intelligence AND stopped to rate potential girlfriends on how "hawt" they'd be around their arms to show to their guy friends, their chances would improve significantly. Odds are, for every guy being friend zoned by a hot girl, there's a girl, not necessarily among the most attractive of ducklings, who's crushing on him right now.