As I posted before, my usual regimen with an I/O was to run it first to heat up the oil. My conclusion with 4-stroke outboards was that I didn't need to because they drained from the bottom and came out cold just fine.
I usually change the oil annually, plus we don't put a ton of miles on the boat each year, so my oil isn't really THAT dirty.
My experience with 4-stroke outboards only goes back to 2017, so my experience is limited. Every year I have been disappointed when I changed the oil because it came out with still a hint of golden, so my thought was I wasted my time and should have kept the old oil for at least another year.
Regardless, back in the day when we ran the outdated I/Os, even hot it flowed like water. My guess is that if your oil came out like a sludge, you waited wayyyyyyy tooooo long to change it.