The thing is, what you're experiencing is pretty much textbook pattern recognition, and it happens to everyone. Tarot cards work a lot like horoscopes - the readings are vague enough that you can map almost any life situation onto them. Your app is literally just shuffling a deck randomly, picking some cards, and serving you an interpretation. Those interpretations are written to be broad on purpose, so they feel personal. When a card says something like "you're at a crossroads" or "change is coming," that applies to basically anyone on any given day, so your brain goes "wow, that's exactly what I'm dealing with."
The weirdly specific feeling you're getting is what psychologists call the Barnum effect - when you believe a generic statement applies uniquely to you. It's not the app being magic, it's your mind doing what minds do, which is look for meaning and connection. Your friends aren't wrong about the algorithm thing, but I'd say there's nothing wrong with using it for fun anyway. Lots of people use tarot or similar tools not because they believe in the supernatural accuracy, but as a way to think through whatever's on their mind. Sometimes just having an external prompt makes you reflect on your own situation differently.
So yeah, it's not giving you actual predictions or tapping into anything real. But that doesn't mean it's useless if it helps you feel better or think stuff through. Just keep it in the "entertainment" category rather than making actual decisions based on what the cards say.