Bruce is supposed to be the doddery, old, bit grumpy, cheesy-joke telling presenter.
That's what he does. Its his act.
He may read autocue badly but I'd rather someone who was able to ad-lib read autocue badly than just another 'generic' younger TV host who can ONLY read autocue, despite how good they are at it.
If something goes wrong, even if it's fluffing his own lines, he can make something of it. That's the advantage of a host like Forsyth who is trained as an all round entertainer and has that experience working directly with audiences, handling heckles.
It isn't supposed to be a straight forward dancing show. It's an entertainment show with dancing. It'd be very bland, in my view, with just a 'straight' autocue reading presenter.
Brucie is the 'face' (the old one at that) of the show and the BBC wouldn't do that if they didn't believe and know through research that he wasn't a hugely popular figure.
Frankly, I don't know what people today complain about. It seems as if anyone who is seen as eccentric or slightly 'off centre' is dismissed in this 'everyone must be Ant and/or Dec' world. Where if something doesn't get read off of an autocue its somehow a sign of 'unprofessionalism'.
Some presenters, the aforementioned Geordie lads included, probably only sneeze and fart when they read instructions to do so off the teleprompter.