Newbie Pilot With Honest Questions & Concerns

Been playing for a few weeks and I honestly enjoy the game overall. Hadn't played a flight sim since Warbirds and Red Baron 3D days because I actually hadn't found a decent flight sim that was period and I enjoyed since then, so you could imagine my joy when I discovered War Thunder! But my joy has especially soured in this last week alone due to what I regard to be the sudden shift in the skill level of random arcade battles. In an apparent blink of an eye I find myself literally surrounded by veteran combat aces - every single opposing player seemingly performing impossible aerial stunts while literally shredding my plane to shreds after a mere couple of shockingly-accurate hits. I went from averaging a comfortable mid-place position in my randomly-assembled teams to just about dead last in the past half-dozen matches. And it's not the fact that I'm losing - I've always been a mediocre player at best at any game I pick up, and am used to that - but suddenly and inexplicably losing quite rapidly at the hands of every single enemy player I encounter after the first two weeks of evenly-matched "win some and lose some" experiences. Please don't mistake this as whining because I'm losing. I just can't figure out how this is happening and am looking for some constructive input as to how I can either better myself as a player, or perhaps fix some deficiency in my mouse controller (I'm quite used to joysticks in my previous flight sims; the mouse is quite new to me in flight sims). Nor am I accusing anyone of cheating; I mean I know I suck, so I'm not even going to suggest that the entire opposite team is cheating because I've been shot down 4 times in a row without landing a single assist kill. I have been steadily adding crew experience points to stamina and g-force tolerance, and yet I cannot comprehend how I can turn as tight as I possibly can at speed and begin to black out while the enemy fighter I'm engaging far below can seemingly turn on a dime, zoom climb, shoot and kill me before I can even complete half a turn. And if this has to do with the opposite player being a more experienced pilot (as well as having an aircraft which far eclipses the abilities of my own) then what game balancing dynamic is throwing my inexperienced butt into the fray against such a higher level of opponent? I'm looking for some input here. I love this game already but if I've already plateaued as a pilot just a mere few weeks into the game, then what's the point of continuing? Is there a reason why my aircraft are refusing to turn despite me nearly blacking out, resulting me in being sitting ducks? Why is my lousy He-100 and BF-109-A1 being spawned in games against 20 Chuck Yeager's flying P-47's and similar? And how come it looks to me that enemy players can snap-turn and aggressively climb regardless of altitude and speed and snipe me? Or am I just hopeless? Don't be shy to say so. It would just confirm the obvious.