Could be down to less pressure? There was alway areas that held these fish but actually getting one was a big risk. One that often wasn’t worth taking. A win was often down to making hemp work in the last hour or backing up a net of Roach with a big Perch or three on choppy.I'm surprised by the amount of catches I see reported on here and on youtube videos of 'big' fish (mostly Bream but Chub and stamp Roach too) on canals these days. Back when I used to fish them even Roach of any size were rare compared to Gudgeon and a bonus fish would usually mean you stood a chance.
I think the fish are probably more confident now with fewer hooks going in the water.