***** NOT A TEACHER *****
Yes, you are 100% correct! CONGRATULATIONS!!!
Most speakers here in the States have thrown in the towel! That is, they now consider "It is me" to be correct. When I say
"most speakers," I include those very well-educated people who give advice on "good" English!
As they say, language is a very democratic matter. The people really do rule. I understand, for example, that some countries
have passed laws limiting the number of English words that are allowed. Of course, the people simply ignore the laws and use
English words that please them.
I am an old man, so I continue to follow the rule: "It is I." But most people say "It is me" because (a) they do not want
people to think that they are "putting on airs" (= I am better educated than you) or (b) they actually think that using "me"
And even when "It is I" was considered correct and used by some people, it was often a social hazard. Could you imagine
what a tough, macho (American) football player would sound like if he said, "It is I"! Why, people would whisper that he
must be a sissy.
A few people want to use "It is I," but social pressure is too strong for them to resist. For example, this very old man has
the courage to say "It is I," but even I do not have the courage to say/write: "Everyone must bring his book." I, too, have
fallen in line and mouth the horrible: bring their book/ his or her book. I am retired, but employed people would find their
jobs in jeopardy if they did not fall in line.
Disclaimer repeated: Not a teacher; these are ONLY my opinions.