You can ask almost any question on Google, or a forum; but there's simply no substitute for having expert eyes upon you as you put theory into practice. Self-study is fine, it is encouraged, but with an expert instructor/mentor you have access to someone who's done
decades of that research...and has seen it applied in the real world. They can see you perform and will know how that performance indicates information you are lacking. They already possess the information you need and how to deliver it to you with relevance to a specific situation or to encourage a certain performance growth or greater understanding.
Nothing on this planet ever gave me a better feel for the real meaning of "buddy distance" than when my deco instructor had me and my buddy swim into the current for a few minutes until I was hoovering pretty hard, then signalled to me that I was out of air.
This is a great example. You can practice all the skills that you read about/see online. You can make yourself very adept at them. However, nothing can replicate the expertise of a good instructor who knows when to challenge you with those drills, skills and contingencies at the worst possible time. As a technical/overhead instructor, I closely study my students and how they are performing throughout the dive. I can time that instant when awareness is low, or stress is high, to throw them the curve-ball that they aren't expecting.... just like Murphy does in real life.
Advanced diving training isn't about learning skills A, B and C. Leave that mindset for the recreational courses... Advanced diving is about learning those skills then applying them...testing them.... as realistically and with as much challenge as possible. Doing so raises performance and eradicates complacency.
You can challenge yourself in self-training, but you are unlikely to ever fully challenge yourself. You can't spot your own moments of weakness and exploit them for a learning benefit.