Phonetic spelling systems are designed to represent the sound of words, not just the ideas. Think of a langauge, like Chinese, that uses a separate symbol for every word. Do you have a clue about how the word is supposed to sound? I doubt it.
We, on the other hand, use alphabets, which are phonetic, and which are supposed to give us help in sounding the word. If the existing spelling does not represent the sound of the word, as well as indicating which word we mean, we are using the alphabet at less than its full capability.
Now, a common spelling of various words is helpful to people who are trained in such systems. It can make it easier to understand which words we mean. However, vocal language changes over time, and if you keep standard spelling, then the spelling of words will gradually depart from the sound, and then we have a system like the Chinese.
Folks who use new spelling, are, in many cases, trying to represent the current sound of the vocal word. In other cases, they are trying to indicate a newness; a difference that is a cultural indicator. It says we are different from the older folks. Older folks complain, because they want to work from the system they are used to. They usually don’t want to learn new language.
Both goals are important. Using standard spelling really helps people be sure they are meaning the same thing. Using invented spelling helps the words become closer to the actual sound. There is a tension between these needs, and thus, we have these arguments. I, btw, am on the side of invented spelling. I do not find it very difficult to understand. Perhaps more importantly, my efforts to learn a new language keeps my brain sharper, compared to remaining mired in the safety of what I know.