What are some of the challenges associated with securing decentralized applications and infrastructure on the web3 decentralized internet?

I summarised the challenges in my free-to-download book here https://www.acs.org.au/insightsandpublications/reports-publications/Blockchain-fundamentals-2022.html.html

The biggest concern for web3, is that it is based on blockchain technology, and user's private keys are stored locally on the user's device, so if the device get hacked/compromised and the attacker obtained the private key, then there is not much the user can do. It is different that web2 since no intermediaries exist to provide recourse in the event of key compromised, for e.g., Web 2.0 providers can revert stolen funds or reset passwords.