LED with wide forward voltage range
If you just get a random LED, then you're right. Setting a "good" value will involve picking a resistor that will not cause too much current to flow in the worst condition (highest voltage rail, lowest resistance, highest/lowest temperature, highest/lowest LED Vf), and then live with the variations.

Note however that they are binned. Each bin has a span of 0.2 volts, making it easier to pick a value.

Depending on your LED source, they might already be binned, and the binning should be indicated on the distributor's listing.