There is nothing inherently wrong with BlueWallet per se. It is in fact one of the most reputable and reviewed pieces of Bitcoin software in the space.
Correct. There is nothing wrong with the bluewallet itself. The problem lies in the installed device Bluewallet.
It's the rationale; smartphones are the worst devices to trust with your bitcoin. There are too many things to account for when it comes to security implications; the integrity of the OS, the apps running in the background etc. It's generally the exact opposite of an air-gapped device; can practically connect to any network at any time.
You are right. This reason made me say that storing large amounts of bitcoin assets in a wallet like Bluwallet and a number of other wallet choices that have a good reputation are a problem that must be carefully thought out.
Because OP said that he could not operate a PC smoothly only able to use the smartphone well, the attention of the vulnerability of the installed device was worthy of attention related to the security.