Writing in all caps is a way to denote yelling. But there's something more important going on here.
People who write things in all caps or don't use paragraph breaks make things very hard to read. This is a basic readability issue for essentially everyone reading it, but it is also particularly hard if somebody has some kind of visual impairment.
White space from (or blue space) from predictable spacing, capitalization and typesetting/writing standards help us all read things better. Even selfishly, if you want people to read what you write you should make it readable.
Does this mean it has to be grammatically correct and perfect? No it does not. The people who will go to the grave over even the smallest of incorrect things are jerks. You may be a high school English teacher during the day, but that doesn't need to propagate to a discussion with other people online. Some of the things you see on social media platforms with crazy abbreviations, lack of capitalization/punctuation, etc. are actually pretty easy to read. Sometimes there is a localized custom and it works.
However, a wall of all caps text is actually kind of hard to read. Nobody likes this, unless you were in the military in the 1950s through the mid 2000s. My dad typed like this for so long because that's how they typed on typewriters and then computers in the Army during his time.
If you're trying to communicate and want people to listen, it really isn't in your best interest to do this.