I'm running 2933 on my Asus Prime X370-Pro, hopefully 3200 when a future update makes it stable.
The issue is dual-rank and double-sided, which is almost all 16GB DIMMs. Just look at the qualified vendor list for ones that are tested to work at their rated speeds.
BTW, it's not MHz for the DDR ratings, but MT/s or MegaTransfers per second. The clock speed is still half the DDR4-xxxx rating, so DDR4-3200 runs at 1600MHz.