I am an adult who takes beginner lessons from a teacher and he says with new students he often has to undo the “learning” from (sometimes years of) those apps - and it can often be devastating to the ego, especially for kids.
Im trying to get my daughter (age 8) into piano and I see the same thing echo on Reddit while doing my research.
It's no different than picking up a ball and playing basketball on your own or tennis...or a simple coding book and making a CRUD app without all the best practices or Code Complete and your fancy frameworks.
I got the exact piano op mentioned on prime day for $150?. I have Simply Piano. My daughter will ask to play the "piano game".
Last summer I signed up my daughter for Ukulele class with a teacher. She barely touched outside what was required assignments.
Yes in the perfect world I have a real piano, with a real teacher who is great with kids who makes it so fun my daughter wants to practice everyday.
But I only have one shot to get her hooked and build momentum.
IMHO passion comes first, then technique. Passion comes from having fun.