Well , I am not expert.......Please correct me If I mention something wrong.....Happy to learn things
As Far as I know ......Non custodial wallet are safe If you know how to properly use them....As there is no centralized server where wallet details is store...so server side hacking is impossible ....like in MT GOX, Bitfinex cases
The things that hack your Non custodial wallet
1) quantum computer
2) You do not download wallet from trusted source .....You download some wrong wallet
3) Your Mobile/Desktop has some sort of malware/spyware
4) You unintentionally leak your seed
except the quantum computer risk....all can be face easily ....If you︀ are careful enough......
Expert comments are welcome