Your best bet would be to use National Banks as example. Bitcoin, unlike National banks allows everyone to download/access the entire software & its very secure database that runs the Bitcoin system in order to be their own banks and jointly help in controlling & regulating the system, whereas Banks only allow few people, such as the banks heads, the access to entire bank database, in order to control and regulate their banks alone.
The ability to download and run the entire Bitcoin system by anyone anywhere in the World, to jointly & equally regulate the system with thousands of people who have exact copy of the system on their personal computers, and to fully control their money/bitcoins in the system is what makes Bitcoin decentralized. The opposite is the case for banks, as only few people are allowed to run & regulate the banks system on behalf of millions of people who have/own money in the banks.
No one anywhere in the world have ultimate control or power over the Bitcoin System thus decision can't be made centrally, unilaterally or by one/few people for the rest of the Bitcoin Network.. A proof to this is that it cannot be shutdown. It continues to operate in other places if a tyrant stops a host from running the system in one part of the world
having an ability for everyone to see the banking laws is different to who gets to activate new banking laws.
having the ability to see everyone elses bank statements, but still control your own fund spending control is different to who sets the rules of what format of payments or financials tools can be used or not.
when you look at bitcoin history. you will see there has been many conflicts over new rules and every time there actually has been a small elite class of devs that do make the decisions and to activate new rules and new financial tools without needing the majority of users to upgrade first to vote/understand or accept the rules. the backward compatible trick means nodes dont need to be network ready to activate a new rule(that alone is a network security risk). thus new rules can be added without network readiness of majority. this means that a certain group which has dominated development has/can and will continue to change thing without mass consent (consensus) or readiness to verify new data types
this has been proven by their actual events of faking a 100%(unnatural but they managed it) compliance even before the actual network of nodes were even ready to understand and verify the new data.
certain people want others to just trust that devs are good hearted and 'just believe' in humans rather than actually scrutinise and verify code/data. however this has not played out well in the many conflicts where anyone not obeying the religion of core dev allegiance is to be treated as the enemy. thus giving ultimate control to core to be the sole proposer of new rules and sole brand to propogate the new rules without requiring majority users abstaining to vote out any potentially bad buggy/cludgy code
the block data is decentralised.. yes
users private key control of their own fund movement is decentralised.. yes
asic mining is decentralised.. yes
but the rule making decisions is done by half a dozen core dev maintainers who make the decisions and they are a central point of failure. their name 'core' is not by accident. nor is their REKT campaigns against anyone not in their allegiance group brand
we should always be reviewing and scrutinising them. if anyone tells you not to worry and just trust a dev, you are ignoring bitcoins main feature. verify, review and check