it's not a bad time to get into this space.there aren't hundreds. I'd say the two biggest are fairly googleable. the platform idea won't work because schools don't have the capital and already have the functionality due to (Anki being open source as you mention,) there's money in the banana stand but it's a tough nut to crack.
There are hundreds of apps based on spaced repetition. How will you be any different?
Agree with OP's argument or not, but practically the entire post is spent answering that question directly.
"Here are some simple examples of how one could make use of collective data."
Sounds like they're going to be a Big Data Aggregator. I look forward to the privacy and security issues.