alot of people think that health records cant be decentralised because there is so much data and it just cant fit on a blockchain.

this is because most people only see the data within a blockchain in the format of a financial transaction:
[in: 1Fr0m4p3r50n value: 0.01btc]
[out: 1t04p3r50n value: 0.01btc]
[signed: 1Fr0m4p3r50n5sign4tur3]

now imagine
[Doctor: 1Fr0m4p3r50n patient: 1t04p3r50n symptom: insomnia result: yes]
[signed: 1Fr0m4p3r50n5sign4tur3]

[Doctor: 1Fr0m4p3r50n patient: 1t04p3r50n symptom: pregnant result: yes]
[signed: 1Fr0m4p3r50n5sign4tur3]

[Doctor: 1Fr0m4p3r50n patient: 1t04p3r50n symptom: HIV result: no]
[signed: 1Fr0m4p3r50n5sign4tur3]