Bitcoin is already not such a useful currency (although it’s currently a very useful speculative asset) due to the fact that it has been maxed out at a real world daily average of ~3.5tx/s for years AFAICT (half the often quote 7tps) as its blocksize is hard-capped (and if history has shown, will never be able to be increased). There are also minimums for value that are effectively spendable based on BTC/byte transaction fees, UTXOs (the set continues to grow dramatically) and price where a larger and larger percentage of the coinbase becomes un-economic to spend as price goes up.

Just as a point of reference, the current median tx price in USD is ~$12, next block confirmations currently cost in excess of 100+ satoshis/byte and the median tx size is ~250 bytes.

Not if the person behind the crime was caught - then their coins could be un-flagged.