Wolf,
I get your frustration. When I first started playing I had a rough time with the vet pilots. Thankfully back then there were plenty of other "baby seals" so I could still get some kills. Now the game is mostly populated with vets - some who fly hundreds of hours each month - and that is a tough environment.
You have basically two choices (IMO) - get better, or start playing the victim card (yelling cheater, etc.). One option will be better for the life of the game and will eventually give you more enjoyment. The other - not so much.
In my 20 plus years of playing I can confidently say nobody is unkillable. There are some who are at the top of their game, but they can all be shot down.
Don't get discouraged - get better. Film all your flights and review what "went wrong." I have found a few of the better players in the game will go to the training arena with you - if you ask. Eventually you will start winning more fights.
Good luck to you.