Actual London resident here
Feels like petty crime is more visible these days. Kids jumping Lime bikes, lads busting the ticket barriers on the tube, that kind of thing. There are parts of town (mostly Oxford Street and the big shopping centres) where if you get spooked by groups of kids on bikes then you might feel uneasy. Having your phone nicked out of your hand by someone on a bike can cause anxiety, especially as the police will do fuck all if it happens. Focus on that and it’s easy to assume the place is turning into something out of Mad Max.
Do I feel unsafe here? Almost never. The tube in particular feels way safer than public transport in other big cities (and it’s way more reliable these days too). My friends and neighbours here don’t spend their days fretting about the city sliding into lawlessness - it’s a bit of an out-of-towner thing really. Affordability is by far and away the biggest issue. But the petty crime stuff is corrosive and like I say, the police should do much more to tackle it, as it has a big impact on visitors in particular.