You do not have a fully defined view of sexism there. One other part of sexism is sexual objectification, which reduces the person or whole gender to an instrument of sexual pleasure, without any view of the person's dignity or humanity.
I just don't share the black-and-white view of the world that you may.
Objectification can be a component of sexism, but in and of itself is not sexist. It is a natural part of human existence demonstrated by both genders on a regular basis in a variety of ways. It is even the entire foundation of initial human attraction. It is not inherently wrong.
Men and women dance at strip clubs. They objectify the customers and the customers objectify the strippers. Hell, my butcher is an object that gives me steak for money and that is all we know of each other. That's okay. You are not obligated to regard everyone as a whole all the time.
We need to stop asserting that every interaction with each person (real or fictional, in person or entertainment) requires a holistic appreciation of every atom of their humanity.
If you objectify all human beings, you share a common trait of sociopaths. If the entirety of your view and interaction with the other gender is based on objectification, then you are probably sexist and have serious issues to deal with. If neither of these are the case, then you are probably a normal human being.
The screen literally just had tits. The whole point of the app was to look at tits. There was nothing else of a woman involved. They really did just take the "tits" part and exclude the rest!
I'm not talking about every guy on the planet. But I think it's very clear that whoever made this app thought, "Know what? We should make an app that just has tits. Nothing else, just tits."
More to the point: the women are being used in a way that is completely determined by the user of the app, instead of being given any kind of consideration as people.
Tits are part of people. I have tits. People have tits and I like people and I like their tits. Without people, there are no tits. How many different ways can I say this? I don't like tits that are disconnected from people. That's disgusting.
If I am staring at a woman's tits - I am certainly giving her whole person my consideration, even though my eyes can only look at one thing at a time. WTF would I do with just a pair of tits?
No, the reason I'm looking is that I probably want more.
I am certainly giving her whole person my consideration
This app removes the women's ability to participate in the exchange at all. They have no control and are presented in a way that is completely in control of the user. When you remove her ability to decide how her body is being used, you are not considering her as a whole person. It's not about tits.