Numbers below follow your paragraphs, quotes are from those paragraphs. I am just replying to a few points, though almost every phrase needs attention.
1) "I think nobody think is impossible to learn it">>> It's not like three people know traditional characters! There are twenty-three million people in Taiwan. Deal with it. Traditional characters are highly learnable; that is as well proven as gravity.
"you must admit">>> No, I don't need to admit what I find incorrect.
While I would say that 个 is easier to learn than 個, educated native readers know in the neighborhood of 4,500 to 5,000 characters (based on my research (character surveys), and my experience). If you want to learn that many characters, then seeing them as a system makes things a lot easier, IMHO. When you have that sort of character vocabulary in traditional and simplified, then you will be qualified to have an opinion. If you just want to take two to four years of university Chinese class, then you will never be able to enter the debate in full because you can't understand what is really happening.
"I can even identify traditional characters that I never seen before without actually trying, by just guessing. " In that case, you are better than most native readers. Amazing!
Yes, traditional characters on a cell phone can sometimes be a problem. Life is difficult; get tough.
2) "ROC contemplated using simplified characters" >>> sort of, in the 1930s, for a moment
The PRC blocked itself internationally. Still does in many ways. Yes, Taiwan got aid, yet there were people so poor there in the 1950s they wore the burlap food sacks from the US as clothing. I am not saying it was common, but it occurred. The PRC was always its own worst enemy. You just have no idea what you are talking about. Taiwan was really poor for many years after WWII. But they emphasized education while the PRC spent 30 years going from witch hunt to witch hunt.
3) You want simplified characters for 人 and 入? What are you talking about? Yes, people confuse certain characters. I do too. I find the problem far worse with PRC forms, even now. Of course, I confuse the written forms of words in English, my native language. Maybe I am just stupid.
"Even me, someone that can be said had no hardships at all and have access to education since 4 years old, didn't realize the difference between 人 and 入 " >>> You had access to education NOT in Chinese, so what does that have to do with learning Chinese as a native reader or you now as a foreigner?
4) First, learn some Korean and Japanese. Second, learn some linguistics. Third, learn about the actual history of the use of Chinese characters in Korea and Japan and the *various* intermediate systems between characters and hangul/kana. You're blabbering on about huge topics that you know nothing about. The various phonetic systems were invented because Korean and Japanese are different LANGUAGES; they are highly inflected, and Chinese is barely inflected at all. Hence, how do you represent those inflections in the writing system? If you bother to research it, you discover it was bloody complicated with Chinese characters.
Latin (as well as Korean, Japanese, and Chinese) is a language. Chinese characters are a writing system (like the Roman Alphabet or Cuneiform). Latin expanded greatly in its use for about 1,000 years under the Romans. It declined because the Romans, who were the only native speakers, lost control.
5) Vulgar in vulgar Latin means common, and that's exactly what it is. People who know Latin find the modern Romance languages a breeze to pick up compared to people who don't know Latin. Gosh, I wonder why that is?
6) Wrong. Traditional characters are formally banned in many contexts such as 99+% of publishing, signage, and education. You should look into The Language Law. They are also widely frowned upon, hence you see posters saying to write in standard (PRC) characters.
"I guess this disdain is politically motivated" >>> Yeah, the Taiwanese in 2017 are frightened of their government and the people in the PRC are free to do as they choose.
"simplified chinese was not invented by PRC but only accelerated its implementation and also, it was rejected a second round of simplified characters, so one can say that is not just simplify for the sake of simplify." >>> They put in far more simplified forms than were ever used together in history, in addition to making at least 20% of the PRC simplified forms. The second round of simplification came very close to happening, but it seems they realized they had already messed up the writing system enough.