Deflation is good for people that have most of their net worth in cash and bad for people that ... don't
Think a little about it: if the money gains in value it would mean their property loses value, because it's price would go down (as the money will be worth more).
Rent seekers mostly have their net worth in assets such as properties and shares, and for those people, inflation is good - because these effectively become more valuable - because they're suddenly worth it's purchasing price + inflation. (That's the definition of inflation, you need more cash to purchase the same product vs deflation where you can buy the same product for less cash).
If every wage etc increased at the same rate as inflation, the difference would probably be academic... But it's not, most employees didn't get a total 30% wage increase within the last 4 years after all, which means that the total purchasing power of (for example) the American people has decreased.
This will ultimately reduce their ability to spend money on products, which means less trades that happen... And more accumulation of wealth, because the people that actually captured that value invested it in things that will effectively become rent seeking, ultimately furthering the spiral