EA have today announced that from the 12 December, the Legacy Edition of the Sims 4 will no longer be available to download. If you want to download the Sims 4 and have a non-Metal Mac, you won’t be able to. Your only option will be to purchase a Metal supported Mac to play the current version of the game on.
Metal info – https://support.apple.com/en-gb/HT205073
Legacy Edition FAQ at Answers HQ – https://answers.ea.com/t5/Technical-Issues-Mac/The-Sims-4-Mac-Legacy-Edition-thread/m-p/8420037
Note – the current EA announcement does not correctly explain what the Metal requirements are for Mac. For clarification, a Mac needs a Metal supported graphics card/chip AND to be running macOS 10.11.6 El Capitan or later. It is not enough to just update the operating system. Hopefully this will be corrected at some point on their website.