If you just dump whole wheat flour in at a 1:1 ratio, you’re asking for trouble. Whole wheat contains the entire grain, including the germ and bran, which absorb way more liquid. That’s why your muffins end up looking like they’ve been on a diet.
Your first move? Hydrate the flour before mixing. Let it sit with the liquid ingredients for 15–20 minutes. This gives the bran time to soften, so your final product isn’t a dry, crumbly mess. (Yes, it feels like you’re making a weird porridge. Embrace it.)