it is randomized and is a 12 word pass phrase for a reason. There are hundreds of thousands of words in the English language that people barely know most of them. Not to mention the combination of the words which could go up to billions. So if you're scared that someone might get to your precious account and take your hard-earned holdings, be at ease knowing that as long as they don't have a quantum computer at hand (not yet released in the public, sometimes existence is even debated if true or not). Your funds are safe.
So I can randomly select 12 words from the 2048 and generate a bitcoin wallet? Thats pretty neat
Humans are usually bad at randomness and good at repeating stuff, so randomly picking words from your brain or some list is not really random.
Easiest way would be using dices or cards, but I saw some crazy stuff people are doing with Geiger's counter recently, because radioactive particles are random.
This is one example of fun and extreme geek tech using python 3 script generating BIP39 mnemonic codes with random data coming from a Geiger counter, and other guy even added RaspberyPi, Audio interface and Americium 241 from a Smoke Detector

https://twitter.com/danieldemercado/status/1437033277358022657?s=21Github:
https://github.com/danieldemercado/GeigerBIP39GeneratorPS
My point is that true randomness is not easy like it seems, but you shouldn't use Geiger's counter for generating your bitcoin wallet if you are a newbie.
Which is why the system does the randomizing for us, so we don't have to use system of counting and randomizing like the Geiger's counter just so we can rest ease that no one with a full working brain could get to our bitcoins and assets in general. People who randomize the words for themselves risk letting their own heuristics and instinctive biases get a hold of their judgement which is very fatal in the crypto world. I am well aware that even if I don't know or notice, some biases tend to leak out of my decisions so for instances like these, I let the machines do the work for me