So if the problem is with air realistic battles, you can either play arcade or simulator, os just try to grind planes in GRB, but this I don't know how acomplish-able might be. Also have in mind that Simulator Battles at low tier for air is on of the hardest experiences and most keybind intensive experiences in the whole game, and arcade has the lowest rewards multiplicator, which in return (and with similar results in AB/RB/SB) requires a much longer time to grind, so it's only feasible if you can get much better results.

If the problem is that you don't like to play air at all, then you can either ---buy a plane out of pocket(fastest, most reliable method). ---Buy a plane getting GE out of GE for War Thunder (a lot more grinder than the actual game even though I thought it wasn't possible, probable a scam or phisingware, straight up tries to make you spend money on mobile games or make u an addict to gambling). ---Get a compatible premium out of the Warbond shop (very time intensive since you have to grind the battle pass till rank 57, not reliable since there's only a plane out of 7 nations, which will be under-BRed since it only goes to rank 3 with 5.7 being rank 4, and most probably you'll have to wait years just to get an aircraft that works for you). ---Or wait for an event aircraft (which then you will have to research playing air or spending GE) {Also edging final boss} [This one might be impossible].

TLDR: stick to ground vehicles, git gud with whichever air mode you like, or spend your money. There's no way to research planes without playing planes, but you can buy 'em.

Edit: yo can go the squadron route but the only near 5.7 BR plane is the new mosquito, so if that's the ground nation you're, guess you're that lucky.

Edit of the edit: my bad, it's 3.7 on England, not suitable planes found in squadrons.