Is there such a thing as an indie dev being blacklisted as a developer from the App Store
First of I would say that it looks like a really nice app that you have produced!

To answer your question: No, I don't think developers are "blacklisted" into having their apps rejected with bogus reasons in order to "bog down" the developer and eventually having them give up on gettings their apps released.

Also, I don't think that you're assigned a specific reviewer that is on a witch hunt for solo developers or anything like that.

However, I do think the realities are that app reviews are done in a very short time frame, and some times the reviewers do not really spend the time necessary to fully understand what a app does - and instead they reject it to be "on the safe side". Also I think the realities are that it is not necessarily the same person reviewing the app each time, so they might not know the history you have.

In order to do something practical and sensible about this, I don't think you'll get anywhere by complaining to Apple that you're being targetted. Instead try making smaller changes to the app and/or description to acknowledge that you're listening to what they are saying (even if you do not agree), and see if that can lead to the app being approved.

For example remove the reference to Google Poly from your app description, and instead change it something neutral like "use it with the most popular 3D modelling API available" or something like that. Then inside your app, you can describe that it is Google Poly.

Similarly try adding an initial intro screen to your app that in simple terms describes how your app works. Make sure NOT to mention QR codes. For example do not say "This app does not require QR-codes". The reviewer might quickly glance at the text and only see "QR-codes" and then reject the app because they haven't gotten a QR-code to test with.