I started using shampoo only once or twice a week (I do shower daily) and just using hot water the rest of the days. My hair is immensely happier now! I also switched to using a "fancy" shampoo with salt granules in it, since the ocean seems to make my hair nice, and that helped as well. Even though the shampoo is more expensive than the cheap stuff I used before, I use way less of it and it's cheaper overall.
I've tested my theory in a couple ways, and it's all been positive. After a Pre-COVID haircut, I had them use whatever shampoo they use for a wash. My scalp was itchy, dry, and uncomfortable for at least 24 hours after that, and my hair was totally flat for a few days as well. I also tried not using shampoo for a long time (3 weeks) and just using hot water, but I got dandruff again and I could feel I was getting dry skin and oil residue building up on my scalp. I'm back to my normal routine now, and have never been happier.