Sounds awful.
The only reason I ride the closest we have to a hilly route once a week is so I don't lag behind too much on group rides where we encounter one or two hills.
Mostly that means repeating a circuit of roller coaster hillettes. Some segments run as steep as 8% but only for short distances, maybe 50-100 yards. The overall average grade is only 1.5%-2% over a two-mile segment, but the actual climbs are much steeper, just for short distances.
On the plus side, it's a pleasant rural route through open prairie, very little traffic other than a couple of intersections. Over a 20-40 mile route I can get in 1,000 ft of total climbing, but it's all roller coasters.
My personal goal is to reach a 10 mph average over the steepest segment, and 16 mph over the 20-40 mile hilly route. Not particularly impressive. I know some local guys who aren't much younger than I who average up to 20 mph over the same segment, faster over the longer route. But they're roadies on lightweight carbon and aluminum road bikes. I'll be satisfied if I can manage 10 mph on that segment on my 1990s hybridized upright mountain bike. Over the past few months my average over the steepest segment has improved from around 6 mph to 8.5 mph, even on days with strong headwinds. So I'm expecting to make that 10 mph goal soon, especially on a calm day. Still won't impress anyone but me, and that's good enough.