How is this going to reduce the apple tax?

Apple provides services for that Apple tax. A new competitor with no ability to create APIs and new tools is not going to compete on quality.

I don’t see what changes this will make. I can see the case for game app stores but regular apps? If apps sell more on the Apple App Store devs will gladly pay some Apple tax.

What apps will we get that are not available now? You need to convince the developers to move platforms, not just the users. So what is the benefit of using a different store?