For physical infrastructure, there are certainly less well maintained areas and historical policies causing issues, but I'm not aware of any areas that are structurally/physically unsafe.
There are 'rougher' areas, places where theft is more likely but very, very few areas that are genuinely unsafe to walk through. The only ones I'm really aware of are two very small areas in London (basically 2-3 buildings) and certain kinds of traveller camps.
For pretty much everything else, it seems to be on par with other European nations - generally behind the Nordics of course.
Share the videos - I'd love to understand where you are coming from.
Everyone knows it, but you're not allowed to say it, and you're definitely not allowed to say it in the UK or you will literally be arrested for speech.
It also wasn't "centuries". The British Crown ruled India (which at the time contained Pakistan and Bangladesh) for less than a century, for instance.
That's far too simply put
The UK has incredible wealth, it is just more concentrated than ever in a few select pockets