I sort of have a tip (I've only played for a few months, but am a 2nd degree black belt in real life) :

Adapt to your opponent. If you opponent is falling on his own, follow him. If he resists, resist back. You should try and stay one step ahead of them. I've had fights where moving one joint differently would have changed the outcome.

You should add some tips on relaxing in the thread. Relaxing is what takes someone from intermediate to advanced.

I quite often lose because I'm short on time and miss a single joint I needed to tweak. There are often times - particularly after being lifted, or during a kick that got you grabbed - where the order you set your actions is important, because if you miss a key part, that can end the fight in one action. If your leg is going to need straightening to keep you upright, do that first, THEN worry about the actions which let you strike back at the opponent. If one arm is needed to keep you from DQing, do that first, then tweak the other hand and legs for whatever else you think you can manage that round.

Also, while I still consider myself a beginner, I'm already seeing the benefits of relaxing joints - rather often in fact.

relaxing does not turn you into a pro. there are different ways to play and everyone has there own style. stick to your style of play and tweak your moves. this will ultimately help you improve.

I never really used tutorials or tested my moves in Singleplayer. I just practiced a lot and eventually got good. xD

The truth is. It's not a question, how to become better. It's straight forward, you don't even need to practice a lot. You don't practice, you play. Playing doesn't make you better, playing a lie.

It's like look at those 2k hours dota guys, they're merely 1500 mmr. Playing a lot doesn't make you great, it's a waste of time. Getting better is about applying effort into becoming more efficient, learning what works that doesn't and why and then developing or stealing and applying strategy, remembering it, saving it in move memory whatever.

The problem why people suck because people don't do this, they don't think I lost because of this and that and could try this or they don't watch how other handle it and imply their methods. They just waste time playing and never work on actually getting better

^^^^^^^^^^^^

someone who practices and applies what they learned for 1 hour will improve quicker than someone who practices lackadaisically for 5 hours. It's all about learning and implying new strategies in this game