If the bush is healthy, then it should still respond well to pruning.
Last winter I cut an old bush down to about 12 ins, this made sure there were at least a couple of dormant buds, on each stem, for regrowth, and it has grown like mad this year. There weren't an awful lot of flowers, tbh, but the bush is back to a healthy size now. I'm expecting it to be back to flowering as usual next summer
Good luck.