They never promised it would be reprint-focused. In the official unveiling stream, they referred to it as "quirky and offbeat," which is something a "Masters" set of reprints would never be called. Then, they go onto saying it's "not a Modern reprint-driven product." The first cards shown made it very clear that they would be playing homage to older cards without actually printing those strong cards into Modern.
Here's the announcement, you can watch it yourself:
https://magic.wizards.com/en/articles/archive/news/announcing-modern-horizons-2019-02-28
If there was a misunderstanding regarding what the set was about, I don't think it's on Wizards. It's on the content creators who talked only about reprints and not about alternatives. Wizards pitched exactly what the set ultimately was when it was announced.