Thanks for reading! Well, it's mostly because I have been heavily spoilt in Shanghai for years.
My first thoughts come to public transport; buses that are infrequent, slow, constantly late and very expensive, trains that are the extreme version of what I just said. Heck, even the underground in london is constantly drowning in delays, which I fell victim to at least 4 or 5 times in the brief time I was there, and it's not like I was using it constantly. The subways have no ability to use phone data, they're tiny and slow, heavily polluted and overcrowded - and you have to pay 20x (literally) the price for the pleasure of it all compared to Shanghai!
Many other aspects apply to things outside of London; most places I've ever known are entirely unchanged since childhood, with the exception of one shop being replaced with some cafe here and there.
And for the most part, it doesn't feel like there are new, vibrant British people, they appear to be all the same people from 20 years or so ago, just older. I don't know where all the youngsters have gone but most of the UK seems to be aging drastically, with the exception of those immigrants coming in from around the world. If you go to 'white' areas, the average age seems to skyrocket to 85 or something!
Finally, I'm spoilt with the culture of WeChat and Alipay, which comes with mega-fast and convenient services the likes of which England will probably never enjoy, and I genuinely think I will have a difficult time adjusting without these things when I eventually go back to England...
All of this, of course, is just my perception in my current spoilt situation though. I'm sure England still has its wonders - and there are many amazing things the 90's has that the 20's doesn't anymore!