You are correct about the limit of OP_RETURN as @ETFbitcoin pointed out but you are forgetting that the examples you used (documents related to ownership of a car or a house, etc.) has centralization attached to it so you don't need to store the whole document on bitcoin blockchain, but only some sort of link to it like a serial number or document hash, etc. and OP_RETURN's 80 byte limit is more than enough for that purpose.

Here is an example of real world application. Land registry by the government of Georgia using bitcoin blockchain:
https://www.forbes.com/sites/laurashin/2017/02/07/the-first-government-to-secure-land-titles-on-the-bitcoin-blockchain-expands-project/

It's funny that the Wired article also mentions a possible solution that I've thought about a bit in the last days. One could make OP_RETURN data completely deletable, for example if their hash is recorded separately. In this case, even a "notify and take down" system could be implemented. The problem would perhaps be that the set of nodes offering the "full" blockchain with the data would decrease, in an extreme (but in the case of BTC, unlikely) case even to zero.