You sent a dozen CVs but didn't receive any positive response. Good news is that it might not be the lack of skills or experience. Bad news is that they will never tell you the truth if...
It's your gender
If you are a woman and they think that only men can perform that kind of job, they will choose a man even though he is less experienced than you.
If you are a man and another candidate is a woman, they will choose a woman to improve their team diversity.
You will never know the real motive, otherwise they will get in legal troubles.
It's your sexual preferences
If you're a gay and don't hide it, some people see risks for their business if they hire you, especially in third world countries, and sometimes those risks are quite real.
It's your age
If you're 45 and older, you have all chances to receive a rejection with a made up reason in third world countries because it's legally prohibited in most places to discriminate by age.
It's your location
If you were born in a sanctioned or “risky” place, it's not your fault, but they won't hire you because their government can punish them otherwise.
I believe you might be even stronger than others because you had to grow up in quite severe conditions, but they will always choose a safer path.
You express unpopular opinions publicly
I think I shouldn't explain to you that freedom of speech doesn't work in real life. Social networks store all your conversations, arguments, party photos, jokes and so on. Recruiters use automated systems to build your full profile which includes everything. And if they notice any suspicious behaviour or unpopular opinions, your CV is under risk to be thrown out into the rubbish bin.
The solution here is to watch your language and behaviour especially on the Internet, of course, if you really need a job.
You're overqualified
This one is my favourite. Do you think only people without experience can suffer from rejections? You'll be surprised then...
In some countries, for example Australia, if they think you have too much experience compared to your potential colleagues, they will likely reject you.
If you think it might be the case and you have a lot of experience in your niche, aim higher and apply for Team Lead, Architect or even Director position instead.
In any case, don't accept silent rejections. Always ask for feedback because it's what helps you improve.
The worst system you could try to fit in is the one that doesn't give you a clear and honest reason for rejection. An example of such a system could be the IELTS language assessment which I took six times a few years ago. The results were always 0.5 point less than I needed for my goal and they never specified what mistakes I made. A paid appeal didn't give any more clarity, so I had to quit that game, and I have no regrets now.
Let me finish on a positive note by telling you the story of a Chinese man named Jack Ma, who was rejected everywhere (universities and multiple jobs he applied) until he, together with his friends, found a company. His Alibaba Group has now become a multi billion dollar company. So sometimes a rejection is nothing but a blessing to do something differently. Think about it, my friend.