Someone needs to tell the semiconductor industry that, then, because all traces inside a modern IC are at 90 degrees. The whole chip is just a big array of parallel lines in two orientation that get cut by photolithography to form circuits. The vias between levels are 90 degrees too, of course.
It's certainly true that electromigration is going to concentrate more at tight bends. But in practice if it isn't killing your 7nm interconnect you're... probably going to be fine with that 1 mil trace that is a million times wider.
Maybe, just maybe, there's a high current, high voltage board out there with tiny traces that was designed with some kind of trivial electromigration mitigation. But if there is, I've never heard of it. And electromigration is absolutely not a reason to avoid 90 degree turns on your digital logic board, don't be ridiculous.
"Electromigration" is the motion of individual conductor nuclei out of the wire due to scattering with electron momentum. Effectively, when electrons are asked (by the electric field in the conductor) to make ultra-sharp turns at nanometer scales, they sometimes collide with the aluminum/copper/tungsten/whatever nucleus instead, knocking that nucleus away from where it should be in the crystal. Over time, this erodes the junction, increasing electrical resistance, and eventually the chip starts to fail at voltages and clock rates it used to handle well.
There are also fun things like optical proximity correction [1], but of course these things are mainly handled automatically by simulations/EDA tools now.
[1] https://en.wikipedia.org/wiki/Optical_proximity_correction
This occurs almost never in a modern VLSI process.
Practically every 90 degree turn in a modern process involves a via or a contact to a different layer--VLSI tends to run different layers in orthogonal directions from one another.
I actually suspect that the really advanced processes nowadays actually ban 90 degree turns in their design rules as it may make the phase shift masks impossible to compute.
The wording was loose, but I stand by the point: there are no interconnect technologies in the modern world that use anything but axis aligned conductors. All turns are 90 degrees. (It's just that to turn 90 degrees in the plane of the wafer you need to make two of them)