Would people 50 years ago accept today’s design trends?

Design trends are never autonomous. They are always responses. Minimalism did not arrive from nowhere. It came as a response to the arts and crafts movement, which itself was a pushback against industrialization making products mass produced and ugly compared to what was there earlier. Industrialization got the cost down. Everybody could afford a lot more products than they could earlier, but those products were not necessarily very well crafted. So there was a pushback, and then the modernistic clean lines came as a response to that.

So the question is not whether people fifty years ago would accept today's trends. The question is what problem today's trends are responding to. Every generation of design carries that cultural baggage. The broader learning is this: good design tries to become true to form, responding to available technologies in the best possible way. That principle does not change across fifty years.