700 Hours and realized I'm trash

Title is pretty self explanatory I feel. Despite the fact that I've done a world conquest, I am really bad at this damn game. I need rehab for my many, many bad habits, and maybe some advice for what to do. Among my problems are that I have almost NEVER made a tank division (and I only ever use the preset tanks) and they never made an impact, I have no idea how to make my airforce work at all, and usually just end up fighting under red air, and I only recently started researching navy tech. Worst of all, I essentially play the game with WWI tactics, but worse. My only divisions are infantry with artillery, usually 25 combat width because I don't really know what it means, always with the superior firepower doctrine, and I just line them up and click battle plan. I almost never micro except for dire circumstances, which is rare, because I usually quit if the game starts going bad in any way. Oh, and I have yet to even complete a historical game on any country. I suppose my question is for one, is this as bad as I think it is, and two, what should I do to get past these and actually enjoy the game more?