If you must solo que, being polite and easy-going is the best approach to getting a group of randoms to work together. Most of the time this works out and especially if you call some simple strats you'll get what is needed. But if you want to be guaranteed friendly working together teammates I suggest finding friends and/or adding randoms in your games that you play that you find out performing on your and the other team. This has worked quite well for me personally.

I don't think there is anything wrong with your play-style, it is an essential part to winning rounds. However, it is good habit to do try out new play styles and ideas whenever you find yourself and you're team struggling.

There is no real one particular thing that separates an MG to an LE. It is mainly just a mixture of having an upper hand on everything. You will find this at all ranks, plus or minus a few outliers.

I personally found the best way to push through the master guardian ranks into the eagle ranks was to just to strive to be better at all aspects of the game. This takes time and dedication. Practicing is essential to getting better and being critical of ones self. There are many other sources out there that have in-depth guides and ideas into getting better at the game which would better help you than myself offering an explanation without going in depth. If you would like me to provide some sources I would be happy to :)

Keep grinding and you'll get there.

Also, may I ask why you believe you aren't 'cutting it' at you're rank?