The more options someone has the pickier they are likely to be. That's indisputable really. Then there are people with no options at all other than to reconcile themselves to being alone. They probably wouldn't appreciate "picky" being used in relation to their situations.
Not necessarily. I know people who have loads of options who aren't picky at all, and I know people with very limited options who are still picky. When I was single, I kept hearing "you're too picky." To that I always replied "I'd rather be alone than be with the wrong person."
Easy enough to sound principled when you're young, partnered up, not having to face the reality of being alone. Combine that with an underlying validation that someone has already considered you ‘worthy’/special.
Actually no, it's not "easy enough" for anyone. It's a harsh reality for a lot of people, but it's there. I stopped being young years ago, and until just over a year ago I wasn't partnered up, and I was totally facing the reality of being alone, as I had my entire life up until then. Also, it's not about principles, it's about preferences. The point remains: Whether or not you have many or few options available to you, doesn't determine whether or not you allow yourself to be "picky." Having few options doesn't automatically result in "I'LL HAVE ANYONE WHO WILL LOVE ME." It certainly didn't for me, and I know several people who are still single, well up in their 40s, and still refusing to just take any living, breathing person that shows interest in them.
If you're talking about avoiding generic 'Hi how are you?' spam, dull CVs or creepy propositions then of course, but that aside, it can still be genuinely difficult to stand out. Most people can put their thoughts in a reasonably coherent manner, but it's harder to do it in ways that convey something distinct about you. Having read thousands of posts on various forums, the majority were more insightful, wittier and said more about the individual in a few words than anything I could have managed in several paragraphs. If the way you express yourself is inherently boring and banal then you are at a clear disadvantage.
Of course it's difficult to stand out, as it is in most situations. The same thing applies for job applicants, auditions, tryouts, etc. It's always about standing out. If it were easy, everyone would do it. So yeah, it's difficult, and it's supposed to be, but to the right person (as in the case of online dating), it could be easy enough. All it would take were a few lines about something you had in common, that the other person seems particularly passionate about. Example: That one guy who wrote me and actually caught my attention, was the only guy to ever mention his interest in gaming, though I had dedicated at least 30% of my profile to that topic. That made him stand out.
Also yes, writing witty and clever messages comes easier to some than others. There are people who struggle with written communication, and for them, online dating might not be the best option. Your last sentence really hits the nail, though. My entire point about this was that, judging from the way the OP described his messages to the women he contacted, they seemed inherently boring and banal. Standing out and being special doesn't have to be long, artistic and overly complex, but it will absolutely require more than repeating the information that's already in your profile.