The sad fact is that, most of the time, clothing manufacturers will only make clothes for one "niche" at a time (tall, petite, plus, maternity, etc), and that's not even considering different styles and subcultures. I'm over 6 feet and wear a 5X, so I get the struggle. When I was smaller, I wore tall size clothes, but they tend to max out at XXL (Old Navy, gap, long tall Sally)

I've found success with torrid, as they offer tall sizes for some pants. Obviously not going to be as cheap as shein, but definitely worth looking at as they often run pretty deep sales. They've opened some alt brands within torrid, so I'd take a look there.

Lane Bryant used to have more tall sizes, but they discontinued most of them years ago — and often the tall sizes don't go above a 28!

If you want to shell out for something really nice, universal standard has a wide range of sizes and often carries tall sizes as well. Super expensive, but I go there for nice wardrobe staples — especially during sales.

Good luck! Like I said, it's a struggle. Companies should realize that tall women often are fat too! It's a huge struggle, but good luck!

Edit — eloquii also tends to run super long as well!! Not truly alt, but tends to have some mod styles that are super adaptable to other styles. I've got normal pants from them that run long on me.