There’s a trick to this. It’s a big of a faff and you’ll think it’s ridiculous, but basically line the crotch of your new jeans with cutoffs from your old jeans.
Genuinely works. At first i thought it’d be unfomfortable, but quite the opposite. You need someone with a sewing machine and a bit of knowhow. No idea how they sew them in without it showing on the outside, but…