They are better than they used to be.
Lots of work has gone into trying to make the RX5700XT cards more stable and that also helped RX Vega 64 and 56.
RX580/480 Polaris GPUs were the biggest sellers for AMD, and received by far the most attention w.r.t. stability and bug fixes.
Your RX580 8GB GPU should be about as stable as it gets.
I own two Gigabyte RX590s - the only 2 slot RX590s I could get.
They were stable enough running games at 2K and 1080p.
They did not work on Blender properly though, and OpenCL support was useless last time I tested them.
I should be checking how they perform next week so I will be running them on Adrenalin 2020 20.3.1 drivers.
Think yourself lucky you did not go through the RX5700XT or Vega 64/56 drivers experience.
Perhaps your Gigabyte RX580 has problems?
Gigabyte do not generally do a great job of AMD AIB GPUs.
Their RX Vega 64 AIB card was particularly bad.