What Would Happen If Bitcoin Had No Difficulty Adjustment?

Without a difficulty adjustment, as more powerful miners join the network, the time it takes to find a block would continuously decrease, leading to an unpredictable and highly volatile block creation rate. This would cause a rapid inflation of the money supply, as blocks would be mined much faster than the intended 10-minute average.

The network's security would also be compromised due to faster confirmation times and less control over the supply schedule.