Non-custodial wallets do not really put users in full control of their keys. That’s because wallets are typically created by, and operated via, someone else’s software or hardware.
That's not wrong. But our tools or dealing with the trust introduced by that are far better than our tools for dealing with custodian trust.
For example, Bitcoin Core doesn't do auto-updates, and does do deterministic builds, precisely to ensure that each and every release has an opportunity for peer.
And the fact is, far more people have lost money from custodians than backdoors inserted into reputable wallets.