Neither I nor any of my family have been tried in China (I am guessing you haven't either), so I cannot comment on the legal system, but in reality, the legal system in the UK is not perfect either. There was a really good book released 2018 about how the legal system is broken here, if you are interested, it's a really good read:

https://www.amazon.co.uk/Secret-Barrister-Stories-Law-Broken...

Onto the topic of the extradition bill though, it specifically excludes extraditing politial dissidents, so it would not streamline the process. What I hear some people say that China will just make some excuses in other areas, which then I don't see the point, since kidnapping and disappearing people would surely be easier right, and since they can already do that, then why would they need the bill? But you know what the bill does allow HK to do, is to extradite a baby murderer to face charges of the crime he commited.

what is the relevance of the UK legal system here? The discussion is about China

Secondly, it could easily be argued that a legal extradition route would be a lot easier than secretly kidnapping and disappearing people over the border. Why do you think it would be easier to kidnap?

Why is the UK legal system relevant here? Well, it's really not, but I am just comparing it to a legal system that I am familiar with, which is a bit of a joke as well; I am happy to hear how the legal system works where you are from if you are willing to tell. Additionally, the Chinese legal system uses civil law, which is based on the Roman system that is used throughout Europe, I mean if I had a spin of it in the UK, can make it look like a horrible system, even though it works.

As for what's easier, let's look at it this way. For me to kidnap someone, I can just find where they are staying, break into said place and then take them away; if I am super careful, I will do it when there is no one around. For me to create a legal extradition route, then I would need to look into your history, financial dealings etc, find out somewhere that looks dodgy, and try to use that as evidence; sometimes I cannot even use that as evidence given it may not even be committed in China. Remember, Al Capone was sentenced not due to the other crimes he committed (due to lack of evidence) but rather due to his tax evasions, so proving something legally when you haven't done it is very hard. If given that you can just go around "kidnapping and disappearing people" as you have stated, why would you want to bother create the legal route right?