Are majuscule and minuscule characters good?

I prefer to read text in sentence case, and get annoyed when people continuously write in lower or upper case. I think majuscule and minuscule are good, but in the right context. I need to research to find out why we write in sentence case and why it is good. Also I would like to find out if other people have a different view to me. Surely the one which would be good in this case would be the case which is most legible to read.