Sadly these are the norm now.
No, it’s certainly not. My kids are 8 and 10 (I really should have come up with more imaginative names) and are certainly not perfectly behaved all of the time, but damn it, they know what good behaviour is and they can pull it out when needed. In a cafe like this, with other people out enjoying themselves, they will be on “best behaviour” and be expected to stay sat down while eating, after which they will probably go outside to burn off their energy where they can’t bother other people. If they have one fault, it’s that they love to meet people and chat with them, so sometimes they need to be told to leave people in peace to eat their lunch, but I try to let them interact when they can as it develops good social skills.
cut the parents some slack – this is how kids are
Some kids are certainly harder to manage than others (I coach kids here for my local club and have seen a good spread of behaviours!) but they should all understand what is expected of them and what “good behaviour” looks like. They won’t always do it (hey, they are kids after all), but I’d expect them to fall back into line with little more than a word from the parents, or have some form of intervention made to explain to them why their behaviour is unacceptable.
I’ve had my own kids for a fair few years and not once have I been told off by another adult for their behaviour and, frankly, I think I’d be mortified if I was!