With constant-sync freely available for the really important files on the cloud (e.g. work docs), the question of how to store the occasional-access important files (e.g. archives of old photos) remain.
Storing these in the constant-sync cloud is too expensive, yet glacial services offered by Amazon is not user/consumer friendly enough. Backup-all-services like Backblaze is great for that anomalous disaster but doesn’t facilitate occasional-access.
I think a dual local medium strategy is sufficient. One copy on your primary computing device, and another copy on an external harddisk. The primary computing device is important enough – and an external harddisk is cheap enough – for the inertia to replace to be very low. Hence it is fair to assume that there will for most-of-the-time be two copies of the data.
The Synology RT1900ac is good value proposition for consumers to further make this external harddisk accessible – for both backing up and occasional-access of the files. A home can have a low-powered NAS for not much more money than what one would spend on a router already.
One of the issues with this strategy is storage on the primary computing device as we take more videos, especially when SSD that are becoming more popular in laptops still lags mechanical drives in capacity-to-price ratio. Perhaps another external harddisk instead of relying on the primary computing device is the solution, but I also think backing up on two harddisks has much higher inertia.