My claim isn't that users don't need secure devices, but rather that there's always a balance between security and other factors (such as repairability), such that locking all parts of a device to it does not make sense for the average user. Hacking someone by replacing a part of their computer/phone with one modified to be malicious is a very target-specific attack.
In comparison, on so-called 'secure' Apple devices, all the usual holes are still open for traditional approaches like vulnerable software, poor password practices etc. These are the approaches that have the widest impact and are the most meaningful to deal with when it comes to security for a broad audience.
As such, it's ridiculous to be suggesting that the security Apple devices add by being unrepairable is reasonable.
In my opinion, it's kind of like how we could force everyone in the world to have a yubikey or other similar separate device for 2FA, with no backups and no recovery methods to eliminate any risk of someone unauthorized gaining access to any data. But that would be way overkill for most people and would make computers much less valuable to them due to all the added hassle. I see Apple's locking down of all parts of the device to prevent repairs the same way.