OP, some users are well-professional writers or they come from countries with good English and writing. Yes, anyone who plagiarised or used AI to generate responses should be punished. But some make use of AI to correct spelling errors, place punctuation marks, commas, or full atop where necessary, and other assistance in writing is not an offense. I know that ost people use grammar as a tool to help them write good English. Do you consider that to be cheating?
That's true. If you feel your written English is not good, and want to improve it, you can use grammar checking tool, AI tools, to improve your post quality in grammar and vocabularies, but that's it.
The core idea for your post is from your brain, and its structure, words are mostly from your brain. Grammarly or AI tools only help you to correct grammar mistakes and use more relevant vocabularies, but it won't change the main content of yours. It means your post content is actually yours and your post won't be red flagged as AI-genrated post.
It's annoying if someone writes in terrible English and posts, members will complain, and if the Engish is clean and excellent members still will complain. Then what do we expect from ourselves?
It is annoying and it's up to these people to improve their written English, to communicate better with other forum members.
They can use whatever tools that are helpful for them to learn Writing and sharpen their Writing skills, including Grammarly, AI etc.