"Could not at least part of the fix needed be done? "

You got it here:

"The state does have $20 million in already-­secured funding that it will use for modest safety-related reconfigurations at the Beltline/Delta interchange starting in 2019, Brindle said. "

Short of building a new bridge across the Willamette ( which get's you into the hundreds of millions in cost area ) there wasn't a whole lot that can beyond the above that would make any difference. It's the bridge that is the main bottleneck, everything else pales in comparison.