For years I couldn't do a single pull up. Not even with poor form. Not even an inch. Zero. I found that so frustrating. It took me a year and a half before I could do my first unassisted pull up. Pull ups are insanely hard. But once you've unlocked them, they are insanely fun. This includes the band-assisted pull up.
One reason why pull ups are so hard is because you're pulling your entire body weight. With a push up, you're only pushing about 60 percent of your body weight. That's because your feet are planted on the ground during a push up. But with a pull up you're lifting your entire body weight vertically with no (or very little) support.
Also, did you know that our pulling musculature tends to be a lot weaker than our pulling musculature? That's why it's easier to train your pushing muscles than your pulling muscles. A lot of activities surrounding daily life involve pushing rather than pulling -- pushing to get off the ground, pushing a grocery cart, pushing to open a door. And so our pulling muscles can get a little bit neglected. Most likely, your push is a little stronger than your pull. Which means that your pull muscles are probably undertrained.
A pull up challenges your strength, your grip, your coordination, and your control all at once. And that's a lot to ask of your body! But that's why it's also so worth it.
If you keep practicing and staying consistent with it, I'm sure you'll be able to get that first pull up.