You are right. I commented on particular things, rather than giving an overall picture.
What I would say is that you have a very large vocabulary and you are ready to experiment with a wide range of sentence structures. The difficulty is that sometimes when you try to use these structures or vocabulary items, they are not completely successful. They are almost correct, but not quite.
One solution might be to simplify. Go back one or two years in your English, and write a sentence that you know to be absolutely correct. Don't try to fit all the vast range of English phrases and words, don't try to translate from your own language, and don't try to experiment too much in an IELTS-exam situation. Instead, try to express the simplest ideas possible.
That's going to be frustrating for you, because you understand the topic, and you want to do it justice. You want to be able to discuss it as fluently as you would in your own first language.
But unfortunately, that's probably being too ambitious.
Instead, rein in your ideas. Simplify, simplify, simplify. Dumb down. Go for the safe option. Imagine that you are writing to your 15-year-old niece or nephew or younger brother or sister. Imagine how little English they know, and imagine also how little they know about anything.
How simply could you express your ideas to them?
A few years ago, the IELTS question used to say something like "write a report for a university lecturer blah blah blah..."
That's history. Now it usually says "give your opinion and examples from your experience."
Well, do, but don't try to do it as well as you could do it in your native language. Take a step back. Simplify. Imagine you are talking to someone who is reasonably good at English, but not too intelligent. Don't try to use the complex ideas you would use if you were with your friends. Instead, throw together six or seven ideas and keep them as simple as possible. Assume nothing. Imagine the examiner is old, and a little slow (you won't be wrong, a lot of the time).
Without joking, I would advise most IELTS Task 2 writers to simplify, simplify, simpliify. It's not the time to try to dazzle. Don't be mechanical and repetitive, because you will end up with a Band 5. But don't try to be too clever, because it won't work. Your complicated idea will tie you into knots and you will fall over. You will desperately try to translate complex ideas from your first language, and you will waste time trying to get them right.
Instead, think of the simplest, most obvious ideas. Throw away the most obvious (the blindingly obvious) but keep the rest. Ask yourself "What is the simplest sentence I can write that will express this idea?" Don't use long words when shorter ones will do. Keep sentences short, on average, but have a mix. Ask (perhaps) one rhetorical question. Interject. Make a sweeping statement, but then back it up in subsequent sentences. Support every idea you put forward with a logical example.
Don't quote anyone else. It's your opinion essay, not a scientist's or a researcher's or a famous psychologist's. Forget about quotes and references. It's not an academic paper.
Give your opinion early and stick to it. Have a thesis sentence which tells us what you are going to say.
In the introduction, tell us what you are going to tell us you are going to tell us. (This is the thesis sentence).
In the body, tell us. Give us your opinion. You might have to spend some time on other people's opinion too, but that is unavoidable, and it can make your essay stronger.
In the conclusion, tell us what you told us. Summarize both sides, and look to the future.
Above all, keep your sentences below 20 or 23 words maximum. Very very few IELTS students can write error-free sentences longer than 20 words.
Aim for an average of 12-15 words per sentence. This means having a mix of long ( 15-20 words ) and short ( 2-10 words ). It's easy to get short sentences right.
Have a mix of short, medium and long. Avoid heavy sentences with a lot of nouns or nominalizations. Try to have as many interesting verbs as possible. If you are in doubt about a phrasal verb (or whatever the grammar teachers call them: "cope with," "impact on," "take part in," etc.,) leave it out and use a regular verb instead ("handle," "affect", "enjoy," etc).
It's just a few hints - some relevant to you, some relevant to other writers. I hope they help.