I couldn’t agree more. It’s the drivers that cannot maintain a constant speed that annoy me most. When driving in a car that has cruise control you do tend to stay quite consistant - however not having this luxury does not excuse inconsistant driving. Stick to a speed and try to stay consistant.
I also love the slow pokes that decide that it’s ok to do 90kmh in a 100kmh zone - but then decide that it is also ok to do 80 in a 60 zone (usually when passing through a small town). I hate that.