So yes, I can see a world where someone uses an app or system like this to avoid conflict to an unhealthy degree. And to be clear, a friend that refuses to meet your extroversion halfway or that demands that you jump through excessive hoops to interact with them is a bad friend, period. But I really disagree that the potential for that kind of abuse means that introversion is somehow a problem. I don't see a difference between boredom and small-scale social anxiety.
There is a well-meaning kind of person that I will occasionally run into that is very interested in getting rid of personality traits I have that they consider problematic. And often I find myself eventually tolerating more quirks in them than they will tolerate in me.
Friendship is, in part, about people accommodating for each other and helping each other -- that's the part that makes friendship special. So I provide affordances for people who get incredibly lonely if I haven't spoken to them in a week, because I recognize they can't just 'act like an adult' and take it at face value that I haven't abandoned them. I provide affordances for people by adjusting my body language, how I talk to them, and where I look while I'm talking to them, because I recognize that some extroverts have trouble emotionally connecting to other people without a lot of extra signals of affirmation. In the same way, I make affordances for people by calling them instead of texting them, because some people place more emotional importance than I do on hearing a voice.
All of this is, to be blunt, crazy. It's just that some people have a random chunk of their brain constantly making them feel anxiety over the fictional idea that "I love you" means more when it's heard in someone's voice then when it's written on a piece of paper.
But generally, we don't describe those people as having a problem. It's not a problem that they have a section of their brains that says, "if someone doesn't make small talk, then that means they're being confrontational or angry." But it is a problem for some reason that I have a section of my brain that says, "if you ask someone for a favor, maybe they didn't actually want to do it, and maybe they might lie about their preferences." And I do kind of regard that as a double standard, because when I accommodate extroverted behavior, I just feel happy to help my friends -- I'm not thinking in the back of my mind, "that person should see a specialist."
I dunno. Every day, everyone here tolerates tons of personality quirks that seem to me to be way, way more crazy, and way more debilitating, and way more problematic for society than something as trivial as being anxious about disappointing friends if a movie night gets canceled.
Any personality trait or quirk, if taken to the extreme, will become a disorder. What is different about introversion that means it's dangerous to accommodate it?
I used to be very introverted and shy, and I still hate doing things like answering the phone or talking in person to people I don't know (and I still work on improving there). But I've learned that communicating with the people around me who care about me (and vice versa) is nothing to be anxious about. It's taken literally decades for me to get here (I now consider myself a somewhat-shy extrovert), but I do feel that my life is better having (mostly) left that anxiety behind. I don't see this as some "personal preference" type of thing; I mean, social anxiety disorder is, well, actually a disorder listed in the DSM.
Your analogy about Candy Crush doesn't really speak to me, because I absolutely agree that there's nothing wrong with killing time with a silly game when you're in a situation where you have to wait (with the exception of games that deliberately and maliciously hook into addictive tendencies). But I do think that an inability/aversion/anxiety around basic communication between friends is actually a problem. I'm not saying that people who have these issues are bad people or anything like that, but I would hope that people with those issues actually view them as issues, and not just a "style of communication" or whatever.
Beyond that, one possibility is that this app just won't gain much traction, and it'll either fail or find a small niche. Otherwise, I just don't see this as something that people will use in moderation. I feel like the people who do genuinely need it (due to introversion or social anxiety or something like that) will use it frequently, and will end up bailing on more activities than they would have otherwise (which sometimes will be good and sometimes will be bad). And I think other people, who don't really have introversion issues, will use it as a way to make rude flakiness easier to justify, and have a normalizing effect on that kind of behavior.