“Why can't people understand me?”

a mispronounced phoneme could result in a misunderstood word.

the misunderstood word could sound like a different object, a different verb, a different tense, a different type of word, and more.

the misunderstood word could result in the boundaries of other words being indeterminable, thereby changing the sound of other words in and around it.

you might mispronounce a word.

you might mis-stress a word or sentence.

you might mis-intonate a word or sentence.

you might use the wrong tense, or you might use the right tense but for slightly the wrong purpose. (This can have crazy knock-on effects.)

you might forget the singular or plural noun or verb form.

you might not hear the speaker's grammar clearly or correctly.

there are so, so many ways that misunderstanding can occur.

Sometimes these misunderstandings are serious, and lead to dangerous problems, or social discomfort, or unintended interactions and relationships.

All of this is not to tell you to be perfect, nor to make you afraid of making mistakes.

It is simply to show you that, as there are so many ways to have confusing interactions, it is vitally important that you try to learn & use the language as well & properly as you can, and that you get out of the mindset of "ah I think my way is good enough, why do I need to use the language in a more complicated way than my language? What is the point of all these tenses and plurals and stuff?"

If these language features were useless, we would have lost them centuries ago.

Besides, whether they are useless or not, we do use them, and that means that our reflexive listening skill depends upon these features being used with the right purpose.

Someone is going to give me shit for writing this, but it's true.

What I see on a daily basis as an English teacher, is loads of students who want to speak English, but have the belief & perspective that all the features of English that don't exist in their native language are simply unnecessary.

This is wrong thinking, and it will result in consistent miscommunication for the rest of their lives.

It also puts unreasonable onus upon the listeners to struggle to decode what they're trying to say in every tiny interaction.