That's why the Feds should be striving to keep workers out of the overwhelmed state UI programs. "Stimulus" now is incredibly cheap, perhaps even negative cost, because the alternative is people sitting at home on the phone for hours, hoping to reach a state UI admin. That is not an exaggeration.
To start with, the Feds should identify existing agencies with the capacity to administer payments. Like the IRS: one coarse-but-quick approach is for the Feds to instruct the IRS to eliminate SSI withholding. That makes it cheaper for every business to employ workers. Beyond that I don't know; this is where Federal leadership should step in.
The tech is definitely old and a few states are still dealing with issues preventing payments but it's rapidly getting fixed. UI is still faster for continued payments than the federal govt, as seen by the pace of the original $1200 stimulus checks which have yet to reach the majority.