As you can tell from my screenname, dog lover here.
You can introduce all these things and there are fines already for fouling parks and streets with dog muck, for not keeping your dog under control, etc.
The simple fact is most owners are responsible and they also have non-aggressive, well socialised dogs. They pick up after them.
But then there's a tier of owner who are fucking clueless, the dog is a fashion , a fad, they don't train them never mind pick up their shit. They are useless and akin to parents who let their kids run wild in busy restaurants with waiters carrying hot food. These people don't care about laws and rules, they think they are above them.
Then their are fuckers , horrible people will continue to own dogs and see them as weapons and wont socialise them, they want them vying for blood, these are the most dangerous, and they don't give. a fuck about laws.
Dogs are just a reflection of the people that own them- most people are good, decent, a minority are feckless and some are just fucking evil.