A chain fork has always been considered. Bitcoin can fork and the most popular chain wins. Satoshi made no secret of that 'democratic' aspect of Bitcoin. It is a feature, not a bug.

So I do not buy the premise of the article that it was never mentioned or considered.

The second point I want to make is that block creation can indeed slow down. If hashing power goes down, it takes longer for the current block to be finished. If hashing power goes way down, creating a new block could take very very long. This is not necessarily a problem. Developers can choose to amend the core program a bit to help getting the current block solved faster (or another type of solution by changing the software a bit) to overcome this obstacle should it ever arise.

So I am not worried about these 'risks' (but FUD sells).